lemon battery research paper pdf

Construction and Evaluation of Electrical Properties of a Lemon Battery

JCBPS; Section C; February 2018 – April - 2018, Vol. 8, No. 2; 092-101, E- ISSN: 2249 –1929 [DOI: 10.24214/jcbps.C.8.2.09201.]

Journal of Chemical, Biological and Physical Sciences

An International Peer Review E-3 Journal of Sciences Available online atwww.jcbsc.org

Section C: Physical Sciences

CODEN (USA): JCBPAT Research Article

Construction and evaluation of electrical properties of a lemon battery

Jakia Sultana, Komor-E-Jahan Dola, Sayed Al Mahmud, Md. Anisur Rahman Mazumder

Department of Food Technology and Rural Industries, Bangladesh Agricultural University, Mymensingh- 2202, Bangladesh

Received: 18 March 2018; Revised: 11 April 2018; Accepted: 18 April 2018

Abstract: The objective of the research was to develop a lemon battery and determine the electrical properties of lemon battery. The main hypothesis of the research work was to determine whether lemon can produce electricity or not. Lemon has a voltaic cell which changes chemical energy into electrical energy. By a series circuit, conductor ( copper ) inserted into lemon to generate voltage . Three varieties of lemon such as Kagoji, Sarboti and Elachi were used for the experiments. Elachi could produce maximum 1.0±0.1 v voltage and 1.25±0.05 mA electricity. Overall, the electricity production was very low due to low amount of citric acid in the lemons . However, lemon could produce minimum electricity which might be used in the Light emitting diode (LED). Keywords: Lemon, battery, voltage, electricity

INTRODUCTION

Citrus fruits belong to the Rutaceae family which are acidic and contain a healthy nutritional content. According to Food and Agricultural Organization (FAO), approximately 40-60% of citrus production 92 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Construction… Jakia Sultana et al. processes for juice production of which 50-60% ends up as wastage. The global citrus waste production was 15-25 million tons a year. Citrus waste creates problem to the environment, thus a sustainable handling of citrus waste is desirable1. Bio electricity generation is reported from waste water using a microbial fuel cell2-4. Lemon, orange and grapefruit are examples of biomass and commonly known as citrus fruit5. They contain citric acid, sugar and other ingredients with sufficient chemical energy that can be converted into electrical energy by means of redox reaction with a specific condition and thus be utilized as batteries to light up light emitting diode (LED) and power up clock or calculator etc6-7. Batteries are containers that store chemical energy, which can be converted to electrical energy or what we called electricity. They depend on electro- chemical reaction to do this. The reaction typically occurs between two pieces of metal called electrodes and a liquid or paste called electrolyte . It is found that the citric acid contained in citrus fruit may act as an electrolyte, which enables the generation of electricity just the same way as a galvanic battery8. There are many variations of the lemon cell that use different fruits or liquids as electrolytes and metals other than zinc and copper as electrodes. A lemon battery is the simplest form of battery. Typically a piece of zinc metal and a copper piece is inserted into the lemon cell and connected by wires. Power generated by reaction of metals is used to power some devices like light emitting diode (LED), digital watch, mobile phone etc. The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta , who used brine (salt water) instead of lemon juice. The lemon battery illustrates the same type of chemical reaction (oxidation-reduction) that occurs in batteries. The zinc and copper are called the electrodes and the juice in the lemon is called the electrolyte. The Fruit is made up of a mixture of chemicals that is called an electrolyte. An electrolyte allows charges to flow. An electrode is the part of a cell through which charges enter or exit. Each cell has a pair of electrodes from conducting materials. There are chemical changes between both the electrodes and the electrolytes. These changes convert the chemical energy to electrical energy. There are two kinds of cells in electricity. There are wet cells and dry cells. Wet cells are liquid cells like the cells in a car battery. A lemon also has wet cells which is a reason why it acts like a battery and is able to produce voltage. A lemon is able to convert to a wet cell when copper and zinc are put into it. Keeping these views into consideration the study was carried out to observe citrus fruit such as lemon as an alternative way to power a light bulb and was to determine the electrical properties such as current, voltage of a lemon battery.

MATERIALS AND METHODS

Electrolyte: An electrolyte is a substance that produces an electrically conducting solution when dissolves in a polar solvent. The dissolve electrolyte separates into cations and anions which disperse uniformly through the solvent. Electrically such solutions are neutral. Three (3) most common varieties of lemon such as Kagoji, Sarboti and Elachi which are available in Bangladesh were used for the experiment to serve as electrolyte due to the citric acid of its. Pieces of zinc sheet metal (annode): In a battery the anode is the negative electrode from which electrons flow out towards the external part of the circuit. The pieces of zinc sheet metal used as the anode.

93 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Construction… Jakia Sultana et al.

Pieces of copper sheet metal (cathode): In a battery the cathode is the positive terminal from which the current flows out of the device. This outward current is carried internally by positive ions moving from the electrolyte to the positive cathode. Multi-Meter (Max Electricity: 99 A, Max Voltage: 999 V): A multi-meter is a digital meter that measures multiple things. It acts like a bunch of different meters put together into one meter. A multi- meter can be used for different purposes. It carries an ammeter, a voltmeter and even a thermometer. An ammeter measures the amount of electrical current that flows through a circuit. To measure current, an ammeter is connected in series with the current. This is so that the ammeter can measure all of the current. The greater the current in the circuit the higher the numbers are on the multi-meter. The multi-meter also carries a voltmeter. A voltmeter is a meter that measures the amount of voltage in a circuit. To measure the amount of voltage in a circuit, the voltmeter is connected parallel to the circuit. It is connected like this so almost no current flows through it. The more volts that the circuit produces, the higher the numbers are on the multi-meter. The multi-meter also carries a thermometer. A thermometer is a meter which measures the temperature. It measures how hot or cold something is. A thermometer measures the temperature of anything. The hotter the temperatures, the higher the numbers are on the multi-meter.

Single cell lemon battery: The preparation of single cell lemon battery was shown in the flow diagram 1.

Piece of copper (plate) was inserted into the one side of lemon

Galvanized nail(zinc) was inserted into the other side of lemon

Wires attached (metal) with copper plate (cathode) and zinc plate (anode)

The wire connected with a multi-meter

The reading were measured from the multi-meter

Reading was positive, connected to an electrical device

Flow chart 1: Lemon battery construction

A sheet of copper plate, a zinc plate, lemon, wires and multi-meter was used to prepare single cell battery. The copper plate and zinc plate were rinsed with a light detergent. The lemon was rolled on a table, applying a small amount of downward pressure. The squeezing action released the juices inside the lemon 94 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Construction… Jakia Sultana et al. needed for the battery to work. The acidity of the juice in a lemon makes it ideal for this sort of chemical reaction. It contains the solution of molecules necessary to carry electric current between the two metal ends of a battery. The slit was needed to be large enough to insert the copper plate about halfway into the lemon. The copper plate was fitted nicely into the slit that have already made. The zinc plate was to be pushed into the lemon about 2 cm away from the copper plate. These items served as the positive and negative ends of the battery. The metals were close to each other in order for the necessary chemical reaction to take place. Using the end clips of the multi-meter, one clip to the copper plate and the other clip to the zinc plate was attached. A small increase in voltage was shown on the multi-meter.

Multi cell lemon battery: In this case, multiple lemon battery was linked together (Figure 1 & 2).

Figure 1: Series connection of lemon battery

A sheet of copper plate, a zinc plate, a lemon (12 nos.), a knife, several wires and multi-meter was to be taken to make a lemon battery. Many lemons were linked together to increase the voltage but not the current. The lemon was rolled on a table, applying a small amount of downward pressure. The squeezing action released the juices inside the lemon needed for the battery to work. Copper-wrapped plate and zinc plate was to be made. A bit of wire was taken and wrapped for a few times around the copper plate and then took the other end and wrapped it around the top of the zinc plate. The copper plate and zinc plate were inserted into separate lemons. The wire was wrapped tightly around each piece. The battery began with a single copper-wrapped plate and end with a single copper-wrapped zinc plate. A piece of wire was to be taken and wrapped it a few times. The wire was wrapped tightly around each piece to make good connections. The slit was large enough to insert the copper plate about half way into the lemon. The copper plate needs to stay firmly in place so make sure the slit isn’t too large. Twelve (12) lemons were lined up and choose one to be the first and one to be the last.

95 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Figure 2: Circuit diagram of lemon battery

The copper-wrapped plate was stuck into the slit that could be cut into the top of the first lemon in the chain. The copper-wrapped zinc plate was inserted into the last lemon in the chain. Each lemon ultimately had one copper plate and one zinc plate stuck out of it. The first lemon in the chain already had a copper plate, the zinc plate was stuck the end of a pair into the first lemon. The second lemon was getting the copper plate from that pair. The second lemon was also getting the nail from the second pair of copper-wrapped plate and zinc plate. Using the end clips of the multi-meter, one clip to the copper wire was attached to the zinc plate and the other clip to the copper wire attached to the copper plate. An increase in the voltage reading was shown on the multi-meter.

RESULTS AND DISCUSSION

Generally, lemon juice contains 5–8% citric acid (Daniel and Charlotte, 1998) and it was the major species undergoing reaction. Overall, the lemon probably produced the most voltage because it has a higher acidity than other citrus fruits. The more the acid in a fruit, the more voltage it produces. Citric acid in a fruit acts like the acid in a battery so the fruit could produce voltage. Three varieties of lemon named Kagoji, Sarbati and Elachi were taken for the experiment. Electrical properties such as-voltage and electricity were measured. The citric acid content of the three varieties of lemon was shown in Figure 3. Effect of lemon varieties on voltage production: Three different varieties of lemon such as Kagoji, Sarbati and Elachi produced minimum amount of voltage which was not sufficient to run any device (Figure 4). However, the average size of a lemon was 37±0.5 g, 89±1.0 g and 130±1.5 g, respectively. The verification in voltage production might be due to the variation in the citric acid. The voltage production depended markedly on the electrode materials.

96 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Figure 3: Effect of lemon varieties on the citric acid content of lemon. Bars represent standard deviation

Figure 4: Effect of lemon varieties on voltage production. Bars represent standard deviation

Effect of lemon varieties on electricity production: One (1) Piece of Kagoji, Sarbati and Elachi produced 1.15±0.05 mA, 1.20±0.1 mA and 1.25±0.05 mA, respectively (Figure 5). There was no significant difference among three varieties of lemon though Elachi produced the highest amount of electricity. However, the electricity produced by all of the varieties was not enough to run high power devices.

97 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Figure 5: Effect of lemon varieties on electricity production. Bars represent standard deviation

Relationship between lemon varieties and voltage production in a series connection: To observe the more significant effect of lemons on voltage and electricity production, lemons were connected in series to power LED (Figure 6).

Figure 6: Series connection of lemon batteries with LED

98 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

The series connection increased the voltage available to devices. Twelve (12) lemons in series connection could be power to a white LED light. The voltage produced from the series connection was 11.9±0.05 v (Figure 7). It was noted that this lemon battery could create enough electrical current to run an LED. Connecting a series of lemons could produce more voltage to run small devices.

Figure 7: Relationship between lemon numbers and voltage production. Bars represent standard deviation

Mechanism and working principal reaction: The cell is providing an electric current through an external circuit, the metallic zinc on the surface of the zinc electrode is dissolved into the solution. Zinc atoms dissolve into the liquid electrolyte as electrically charged ions (Zn2+), leaving 2 negatively charged electrons (e−) behind in the metal: 푍푛 → 푍푛2+ + 2e- [1] This reaction is called oxidation. While zinc is entering the electrolyte, two positively charged hydrogen ions (H+) from the electrolyte combine with two electrons at the copper electrode's surface and form an uncharged hydrogen molecule (H2):

+ − 2H + 2e → H2 [2] This reaction is called reduction. The electrons used for the copper to form the molecules of hydrogen are transferred by an external wire connected to the zinc. The hydrogen molecules formed on the surface of the copper by the reduction reaction ultimately bubble away as hydrogen gas. Figure 8 showed the probable atomic model for the chemical reactions. Zinc atoms enter the electrolyte as ions missing two electrons (Zn2+). Two negatively charged electrons from the dissolved zinc atom are left in the zinc metal. Two of the dissolved protons (H+) in the acidic electrolyte combine with each other and two electrons to form molecular hydrogen H2, which bubbles off of the copper electrode. The 99 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

Construction… Jakia Sultana et al. electrons lost from the copper are made up by moving two electrons from the zinc through the external wire.

Figure 8: Probable atomic model for chemical reaction in lemon cell for the construction of a lemon battery

There was a chemical reaction between the steel in the zinc plate and the lemon juice. There was also a chemical reaction between the copper plate and the lemon juice. These two chemical reactions pushed electrons through the wire. The amount of voltage produced by one (1) lemon was not strong enough to power up devices. At least four (4) lemons were needed to power an LED bulb. Using twelve (12) lemons in series connection were enough to power a white LED light. This result will be important to people when their power goes out and they can use some lemons to power a light bulb for light. By multiplying the average electricity of a lemon (1 mA) by the average (lowest) voltage (potential difference) of a lemon (0.7 V) it can be concluded that it would take more than 100 lemons to run a mobile phone.

100 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

1. R. Wikandari, R. Millati, M.N. Cahyanto, M.J. Taherzadeh, Biogas production from citrus waste by membrane bioreactor. Membrane. 2014, 4, 596-607. 2. A.M. Khan, Electricity generation by microbial fuel cells. Adv. Natur. App. Sci. 2009, 3 (2), 279- 286. 3. A.M. Khan, Generation of electricity by the aerobic fermentation of domestic waste water. J. Chem. Soc. Pak. 2010, 32 (2), 209-214. 4. A.M. Khan, Correlation of COD and BOD of domestic waste water with the power output of bioreactor. J. Chem. Soc. Pak. 2010, 32 (2), 269-274. 5. M.A. Randhawa, A. Rashid, M. Saeed, M.S. Javed, A.A. Khan and M.W. Sajid, Characterization of organic acids in juices of some Pakistani citrus species and their retention during refrigerated storage. J. Ani. Plant Sci. 2014, 24(1), 211-214. 6. P.B. Kelter, J.D. Carr, T. Johnson, C.M. Castro-Acuna, Citrus spp.: orange, mandarin, tangerine, clementine, grapefruit, pomelo, lemon and lime. J. Chem. Edu. 1996, 73 (12), 1123-1127. 7. J. Goodisman, Observation on lemon cells. J. Chem. Edu. 2001, 78 (4), 516-518. 8. H.L. Oon, A simple electric cell, chemistry expression: An inquary approach. Panpac education Pvt. Ltd. Singapore, 236-250.

Corresponding author: Md. Anisur Rahman Mazumder Department of Food Technology and Rural Industries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh Email: [email protected] Online publication date: 18.4.2018

101 J. Chem. Bio. Phy. Sci. Sec. C, February 2018 – April - 2018, Vol. 8, No. 2; 092-101 [DOI: 10.24214/jcbps.C.8.2.09201.]

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Lemon Battery Experiment

The lemon battery experiment is a classic science project that illustrates an electrical circuit, electrolytes, the electrochemical series of metals, and oxidation-reduction (redox) reactions . The battery produces enough electricity to power an LED or other small device, but not enough to cause harm, even if you touch both electrodes. Here is how to construct a lemon battery, a look at how it works, and ways of turning the project into an experiment.

Lemon Battery Materials

You need a few basic materials for a lemon battery, which are available at a grocery store and hardware store.

• Galvanized nail
• Copper penny, strip, or wire
• Wires or strips of aluminum foil
• Alligator clips or electrical tape
• An LED bulb, multimeter, digital clock, or calculator

If you don’t have a lemon, use any citrus fruit. A galvanized nail is a steel nail that is plated with zinc. The classic project uses copper and zinc because these two metals are inexpensive and readily available. However, you can use any two conductive metals, as long as they are different from each other.

Make a Lemon Battery

• Gently squeeze the lemon or roll it on a table to soften it. This helps the juice flow within the fruit.
• Insert the copper and zinc into the fruit. You want the maximum surface area in the juicy part of the fruit. The lemon peel helps support the metal, but if it is very thick and the metal does not reach the juice, scrape away part of the peel. Ideally, separate the metal pieces by about 2 inches (5 centimeters). Make sure the metals are not touching each other.
• Connect a wire to the galvanized nail using an alligator clip or electrical tape. Repeat the process with the copper item.
• Connect the free ends of the wire to an LED or other small electronic device. When you connect the second wire, the light turns on.

Increase the Power

The voltage of a lemon battery is around 1.3 V to 1.5 V, but it generates very little current. There are two easy ways of increasing the battery’s power.

• Use two pennies and two copper pieces in the lemon. You don’t want any of the metal pieces within the fruit to touch. As before, connect one zinc and one copper piece to the LED. But, wire the other zinc and copper to each other.
• Wire more lemons in series with each other. Insert a nail and copper piece into each nail. Connect the copper of one lemon to the zinc of the next lemon. Connect the nail at the end of the series to the LED and the copper at the end of the series to the LED. If you don’t have lots of lemons, you can cut up one lemon into pieces.

How a Lemon Battery Works

A lemon battery is similar to Volta’s first battery, except he used salt water instead of lemon juice. The zinc and copper are electrodes. The lemon juice is an electrolyte . Lemon juice contains citric acid. While both salts and acids are examples of electrolytes, acids typically do a better job in batteries.

Connecting the zinc and copper electrodes using a wire (even with an LED or multimeter between them) completes an electrical circuit. The circuit is a loop through the zinc, the wire, the copper, and the electrolyte, back to the zinc.

Zinc dissolves in lemon juice, leaving zinc ions (Zn 2+ ) in the juice, while the two electrons per atom move through the wire toward the copper. The following chemical reaction represents this oxidation reaction :

Zn → Zn 2+  + 2e −

Citric acid is a weak acid, but it partially dissociates and leaves some positively charged hydrogen ions (H + ) in the juice. The copper electrode does not dissolve. The excess electrons at the copper electrode combine with the hydrogen ions and form hydrogen gas at the copper electrode. This is a reduction reaction.

2H + + 2e −  → H 2

If you perform the project using lemon juice instead of a lemon, you may observe tiny hydrogen gas bubbles forming on the copper electrode.

Try Other Fruits and Vegetables

The key for using produce in a battery is choosing a fruit of vegetable high in acid (with a low pH). Citrus fruits (lemon, orange, lime, grapefruit) contain citric acid. You don’t need a whole fruit. Orange juice and lemonade work fine. Potatoes work well because they contain phosphoric acid. Boiling potatoes before using them increases their effectiveness. Sauerkraut contains lactic acid. Vinegar works because it contains acetic acid.

Experiment Ideas

Turn the lemon battery into an experiment by applying the scientific method . Make observations about the battery, ask questions, and design experiments to test predictions or a hypothesis .

• Experiment with other materials for the electrodes besides a galvanized nail and copper item. Other common metals available in everyday life include iron, steel, aluminum, tin, and silver. Try using a nickel and a penny. What do you think will happen if you use two galvanized nails and no copper, or two pennies and no nails? What happens if you try to use plastic, wood, or glass as an electrode? Can you explain your results?
• If you have a multimeter, explore whether the distance between the electrodes affects the voltage and current of your circuit.
• How big is the effect of adding a second lemon to the circuit? Does it change the voltage? Does it change the current?
• Try making batteries using other foods from the kitchen. Predict which ones you think will work and test them. Of course, try fruits and vegetables. Also consider liquids like water, salt water, milk and juice, and condiments, like ketchup, mustard, and salsa.

The lemon battery dates back to at least 2000 years ago. Archaeologists discovered a battery in Iraq using a clay pot, lemon juice, copper, iron, and tar. Of course, people using this battery did not know about electrochemistry or even what electricity was. The use of the ancient battery is unknown.

Credit for discovery of the battery goes to Italian scientists Luigi Galvani and Alessandro Volta. In 1780, Luigi Galvani demonstrated copper, zinc, and frog legs (acting as an electrolyte) produced electricity. Galvani published his work in 1790. An electrochemical cell is called a galvanic cell in his honor.

Alessandro Volta proved electricity did not require an animal. He used brine-soaked paper as an electrolyte and invented the voltaic pile in 1799. A voltaic pile is a stack of galvanic cells, with each cell consisting of a metal disk, an electrolyte layer, and a disk of a different metal.

• Goodisman, Jerry (2001). “Observations on Lemon Cells”. Journal of Chemical Education . 78(4): 516–518. doi: 10.1021/ed078p516
• Margles, Samantha (2011). “ Does a Lemon Battery Really Work? “. Mythbusters Science Fair Book . Scholastic. ISBN 9780545237451.
• Naidu, M. S.; Kamakshiaih, S. (1995). Introduction to Electrical Engineering . Tata McGraw-Hill Education. ISBN 9780074622926.
• Schmidt, Hans-Jürgen; Marohn, Annette; Harrison, Allan G. (2007). “Factors that prevent learning in electrochemistry”. Journal of Research in Science Teaching . 44 (2): 258–283. doi: 10.1002/tea.20118
• Swartling, Daniel J.; Morgan, Charlotte (1998). “Lemon Cells Revisited—The Lemon-Powered Calculator”. Journal of Chemical Education . 75 (2): 181–182. doi: 10.1021/ed075p181

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July 23, 2015

Generate Electricity with a Lemon Battery

A tingly science project from Science Buddies

By Science Buddies

Did you know you can make a battery out of a piece of fruit? You'll be charged up on science when you feel the success of your homemade electricity! 

George Retseck

Key concepts Electricity Batteries Electrochemical reaction Electric conductor

Introduction Can you imagine how your life would change if batteries did not exist? If it were not for this handy way to store electrical energy, we would not be able to have all of our portable electronic devices, such as phones, tablets and laptop computers. So many other items—from remote-control cars to flashlights to hearing aids—would also need to be plugged into a wall outlet in order to function.

In 1800 Alessandro Volta invented the first battery, and scientists have been hard at work ever since improving previous designs. With all this work put into batteries and all the frustration you might have had coping with dead ones, it might surprise you that you can easily make one out of household materials. Try this activity and it might just charge your imagination!

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Background Batteries are containers that store chemical energy, which can be converted to electrical energy—or what we call electricity . They depend on an electrochemical reaction to do this. The reaction typically occurs between two pieces of metal, called electrodes , and a liquid or paste, called an electrolyte . For a battery to work well, the electrodes must be made up of two different types of materials. This ensures one will react differently than the other with the electrolyte. This difference is what generates electricity. Connect the two electrodes with a material that can transport electricity well (called a conductor ) and the chemical reactions fire up; the battery is generating electricity! As you make connections, note that electricity likes to take the path of least resistance. If there are multiple ways to go from one electrode to the other, the electricity will take the path that lets it flow most easily.

Now that you know the essentials of a battery, let's examine some household materials. Aluminum foil is a good conductor—electricity flows easily through it. The human body conducts electricity as well, but not as well as aluminum foil. Electrodes are as common as copper pennies you might have stashed in your piggy bank. As for electrolytes, they are found all over the kitchen; lemon juice is just one example. A simple household battery might be easier to make than you imagined!

At least two pennies

A few drops of dishwashing soap

Paper towels

Aluminum foil (at least nine by 60 centimeters)

At least one lemon (preferably with a thin skin)

Knife (and an adult's help when using it)

At least two plastic-coated paper clips

Preparation

Wash your pennies in soapy water, then rinse and dry them off with a paper towel. This will remove any dirt sticking to them.

Carefully cut three aluminum foil rectangles, each three centimeters by 20 centimeters.

Fold each strip in thirds lengthwise to get three sturdy one-centimeter-by-20-centimeter aluminum strips.

Note: In this activity you will make a very low-voltage battery. The amount of electricity generated by this homemade battery is safe, and you will even be able to test it by touching your finger to it and feeling the weak current. Higher voltages of electricity, however, can be very dangerous and even deadly; you should not experiment with commercial batteries or wall outlets.

Place the lemon on its side on a plate and have an adult carefully use the knife to make a small cut near the middle of the lemon (away from either end). Make the cut about two centimeters long and one centimeter deep.

Make a second, similar cut about one centimeter away and parallel to the first cut.

Push a penny in the first cut until only half of it is showing above the lemon skin. Part of the penny should be in contact with the lemon juice because that is what serves as the electrolyte. This copper penny in contact with the lemon juice serves as your first electrode. Note: If your lemon has a very thick skin, you might need an adult to carefully cut away some lemon peel. Why do you think is it important for part of the penny to be in contact with the lemon juice?

Slide one of the aluminum strips in the second cut until you are sure part of the aluminum is in contact with the lemon juice. Can you guess which part of a battery the aluminum strip that sits inside the lemon is? Do you think it is important for the aluminum to be in contact with the lemon juice?

You have just made a battery! It has two electrodes made of different metals and an electrolyte separating them . Do you think this battery is generating electricity or is there still something missing?

Your battery can generate electricity but will only do so when the electrodes are connected with something that conducts electricity. To make a connection attach the second aluminum strip to the part of the penny sticking out of the lemon with a plastic-coated paper clip. Make sure the aluminum touches the penny so electricity can pass between the copper and aluminum. You used an aluminum strip to create a connection; would you expect a plastic strip to work as well? Do you know why you do not need to create a connection to the second electrode for this particular battery?

As soon as the two aluminum strips touch one another, electricity will be produced in the battery and flow through the strips, from one electrode to the other. Because you cannot see the electricity flowing, you can try to feel it. Keep the two strips about one centimeter apart and touch your fingertip to them. Can you feel a tingling, created by a small amount of electricity running from one aluminum strip to the other through your body ?

For more electrical juice (and slightly stronger tingling sensation), you can build a second battery, identical to the first. You can choose a different spot on the lemon you just used or use a second lemon to build a second battery. Note that you only need one aluminum strip to build a second battery. To connect the second one to the original find the aluminum strip of the first battery that serves as electrode. (It has its end inserted in the lemon.) Use a plastic-coated paper clip to attach the other end of this aluminum strip to the penny of the second battery. This connects the aluminum electrode of the first battery to the copper electrode of the second battery.

Test this set of connected batteries in a similar way as you tested the single battery, bringing the ends of the two aluminum foil strips sticking out of your battery set (those that have a free end) in contact with your fingertip. Can you feel electricity running? If you could feel it well the first time, is this any different? (Note: If you cannot feel the tingling sensation, check if each electrode—pennies and the aluminum strips stuck in the lemon—are inserted deep enough so they are in contact with lemon juice; make sure there is firm contact between the penny and its attached aluminum strip; and that the aluminum strips are not touching one another. If all is correct, maybe you need slightly more electricity to feel tingling. You can test another person to see if he or she can feel the electricity or you can opt to add one more lemon battery to your set.)

Extra: Now that you can detect whether electricity is generated or not, try some different configurations. What happens if you let the aluminum strips touch? What happens if you replace an aluminum strip with a plastic piece, an unfolded metal paper clip or a toothpick?

Extra: Scientists call the way you connected your batteries in this activity "connecting batteries in series." Do you think the way you connect two batteries makes a difference in the amount of electricity you felt? Try it out by connecting the two copper electrodes to one another and attaching the two aluminum electrodes in the same way. (Note: You will need an extra strip of aluminum to do this.) Scientists call this "connecting batteries in parallel." Test both ways of connecting batteries and compare. Do you feel a difference?

Extra: Try different types of metals as electrodes for your batteries. Do you think a battery with two pennies as electrodes would generate electricity? What about a battery with a penny and a nickel ? Note that some combinations might generate electricity but the amount generated might be below your ability to feel it. Connecting two or more of these batteries might help you identify good combinations.

Extra: You used a lemon to provide the electrolyte for your battery. Do you think other vegetables or fruits would work as well? Would a potato, apple or onion battery work? Try a few from around the kitchen (with permission, of course). Does one particular fruit or vegetable outperform the others? With what you learned about how batteries generate electricity, why do you think that one type of produce made a stronger battery?

Extra : If you have an LED (light-emitting diode) available, investigate how many lemon batteries are needed to light it.

[break] Observations and results Did you feel the tingling in your fingertip?

The battery you just made has a copper and an aluminum electrode separated by electrolyte lemon juice. It will generate electricity as soon as the electricity has a path to flow from one electrode to the other. You created this path using strips of aluminum, a material that conducts electricity well.

By connecting your battery to your fingertip, you allowed the small amount of electricity it generates to run through your body. This amount of electricity can create a tingling feeling in a fingertip. Experiences will differ from person to person. Some people might only feel the bigger signal generated by connecting several batteries in a particular way. Letting the aluminum strips touch provides a very easy way for the electricity to run from one electrode to the other, so almost no electricity will travel through your body and the tingling sensation disappears. Plastic and wood do not conduct electricity well; none will be felt when using these materials as connections. Metals, on the other hand, conduct electricity well. Different combinations of metals as electrodes will influence the amount of electricity generated. Using identical metals as electrodes will not generate electricity, however.

In this activity you made a very low-voltage homemade battery. But using commercial batteries can be dangerous—and never experiment with wall outlets!

More to explore Batteries , from ExplainThatStuff! How Do Batteries Work? , from LiveScience A Battery That Makes Cents , from Science Buddies Potato Batteries: How to Turn Produce into Veggie Power! , from Science Buddies

This activity brought to you in partnership with Science Buddies

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• Lemon Battery

🍋This is an experiment to demonstrate how lemony chemical energy can be turned into electrical energy! 

🍋This lemon battery is based on a similar concept as the very first battery, built by Alessandro Volta in 1799!

🍋The battery works by moving electrons (little charged particles) from anode (negative: zinc metal, paper clip or a galvanised nail) to cathode (positive: copper metal, e.g. a penny coin) via the fruit.

🍋If you set up your circuit correctly, you will be able to see it powering a small LED light.

🍋Instead of lemons, you can also use other citruses (limes, oranges, grapefruits), or other acidic fruits. You can also use potatoes, they have a different chemical (phosphoric acid instead of citric acid) that allows them to power the battery. 

🍋To make this battery work better, you can roll the fruit by such making it juicier inside or, if using a potato, part boil it.

🍋You can also use acidic liquids, such as vinegar (acetic acid) instead of lemons.

🍋The more lemons/fruit (AKA battery cells) you hook up, the more powerful this battery will be! 

Here is a photo from Hope set up by Alessia, that she then demonstrated on a call!

And here is a PDF of the experiment - please read it before doing the experiment!

EXPERIMENT_LEMON_BATTERY.pdf

So, which makes a better battery: 🥔POTATOES or 🍋 LEMONS? Here is a video!

🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋🍋

And this is currently the BIGGEST lemon battery!

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When Life Gives You Lemons...Make A Battery

Emily Kwong

Rebecca Ramirez

Madeline K. Sofia

Electrical circuit with lemons. A chemical reaction between the copper and zinc plates and the citric acid produces a small current, that is able to power a light bulb. Science Photo Libra/Getty Images hide caption

Electrical circuit with lemons. A chemical reaction between the copper and zinc plates and the citric acid produces a small current, that is able to power a light bulb.

We're going "Back To School" today, revisiting a classic at-home experiment that turns lemons into batteries — powerful enough to turn on a clock or a small lightbulb. But how does the science driving the "lemon battery" show up in those household batteries we use daily?

Short Wave host Maddie Sofia and reporter Emily Kwong speak with environmental engineer Jenelle Fortunato about the fundamentals of electric currents and the inner workings of batteries.

Fortunato is a postdoctoral researcher at North Carolina State University studying materials for electrodes that can be used in solid-state batteries.

A few years ago, she brought the "lemon battery" to classrooms through Penn State's Science U program. Middle schoolers got particularly invested in the experimental possibilities.

"They hooked up like 20 lemons, three cups of lemon juice, an apple, three different light bulbs and a buzzer buzzing. And it was... it was chaos...I was in awe. Leave it to kids to come up with something like that," Fortunato said.

You can build your very own lemon battery using Science U's design here , written by Fortunato and Christopher Gorski of Penn State College of Engineering.

A reminder: Do NOT play with household batteries. Be safe out there, scientists!

You can read more about Fortunato's research here .

This episode was produced by Rebecca Ramirez, edited by Viet Le and fact-checked by Rasha Aridi. J. Czys and Josh Newell were the audio engineers. Special thanks to Short Wave listener Violet Thomas for inviting us to dig deeper into battery science.

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• Page ID 131417

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• Insert the Cu and Zn electrodes into the fruit.
• Connect the metal clips to an LED light and see it glow (light is dim, so you may need to turn off the lights).
• Clips may also be attached to a watch to see the seconds hand move or to a voltmeter to measure the voltage
• Increasing the number of fruit will create a high voltage
• Be sure to wipe down the electrodes with a paper towel after use

Discussion:

The current derives from the oxidation of Zn metal and the reduction on H + ions. Zn atoms dissolves in the acidic citrus juice leaving 2 negatively charged electrons (e - ) behind in the Zn anode.

Zn → Zn 2+ + 2 e -

As Zn enters the solution, 2 positively charged H + ions pick up 2 electrons at the Cu cathode and form H 2 gas.

2H + + 2e - → H 2

The electrons lost by Cu are replaced by 2 e - from the Zn anode that have traveled through the wire. The electrical current is produced by the movement of electrons in the circuit. During oxidation, Zn looses electrons to reach a lower energy state; the energy released provides the power to turn on the LED, start the watch, etc.

Disposal (by Storeroom)

Used lemons can be tossed in the trash.

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Lemon Batteries

Can you get power from a lemon?

Batteries consist of two different metals suspended in an acidic solution.

Is it possible to use the acid in a lemon to power a light? Try it to find out!

Watch the video on YouTube: QYZE-SrpoJ4

You Will Need

4 or more large, fresh, juicy lemons or other citrus fruits

A kitchen knife

4 or more zinc electrodes You can find galvanized washers or roofing nails at most hardware stores, or you can purchase either zinc or magnesium wire online

4 copper electrodes Copper-coated pennies work, or you can find bare copper wire or copper plumbing fittings at most hardware stores

1 light-emitting diode (LED) component We recommend a red LED because they typically need lower voltages to glow than other colors, but many colors will work. The best LEDs for this experiment are designed to glow with a low current such as this set from Amazon , or you can purchase a lesser quantity from Mouser electronics .

6 or more lead wires with alligator clips. Such as this set available on Amazon

Multimeter (optional)

Materials & Directions PDF

NOTE: Some retailers also sell lemon battery kits that can include a buzzer or a low voltage clock. These instructions assume you are using your lemon battery to make an LED glow.

• Ask your scientist to create a testable question.
• Carefully clean your zinc and copper electrodes to remove any dirt or grease. (Careful not to scrub all of the zinc coating off the galvanized washers or nails.)
• Roll one lemon on a hard surface while pushing down to break the cell walls and loosen up the juice inside. The sour (acidic) juice is needed for the chemical reaction that you are about to start.
• Place the lemon on its side on a plate and have an adult carefully use the kitchen knife to make a 2 small cuts in the top of the lemon. Make each cut about two centimeters long, one centimeter deep, and about 0.5-1 centimeters apart. (To conserve lemons, you can cut 1 lemon in half, and put the electrodes in either the cut side or the rind side.)
• Insert one zinc electrode deep into one of the cuts, and one copper electrode deep into the other. Leave some sticking out so you can connect your wires to them. You have now made a lemon cell!

• Set the multimeter to measure DC voltage (V with a straight line). If it has scale options, set it to measure 2000 millivolts (2000m).
• Hook two alligator clips from your leads to the two electrodes. Attach red lead of the multimeter (+) to the copper electrode, and the black lead of the multimeter (-) to the zinc electrode.
• Measure the voltage from your lemon cell. The average lemon cell should read about 0.9–1.0 volts.
• Now set the multimeter to measure current (A with a squiggly line: mÃ/Ã). If it has scale options, set it to measure 1–20mÃ.
• Measure the current of your lemon cell. It should read a few tenths of a milliampere. Some multimeters are not sensitive enough to measure currents less than one milliampere, in which case you will see 0.0 as the reading.
• A red LED typically needs a voltage of 1.2–1.6 V, so we need more power to light the bulb.
• Follow steps 3-5 to make 3 or 4 more lemon cells.
• (Optional) If you have a multimeter, check each lemon battery to make sure it generates voltage and current.
• Connect the zinc electrode on the first lemon to the copper electrode on the second lemon.
• Connect the zinc electrode on the second lemon to the copper electrode on the third lemon.
• Repeat if using more lemons. This type of connection is called a series circuit , and provides one path through which electricity can flow.
• Gently bend the lead wires of the LED apart from each other.
• Connect a lead wire from the copper electrode of the first lemon cell to the longer lead wire from the LED.
• Connect a lead wire from the zinc electrode of the third cell to the shorter wire of the LED.
• Turn down the room lights to see if your LED is glowing! If it isn’t, see the troubleshooting tips below.

Troubleshooting your lemon battery:

• Ensure the electrodes are not touching inside lemon.
• Ensure the alligator clips on the test lead wires are not touching each other where you connect them to the LED.
• The wires from one lemon to the other have to be connected from zinc to copper in order for the electricity to flow.
• Is it an old lemon? The lemon needs to be juicy inside.
• Do you need to add more lemons?
• Is your LED broken? Or does it require a higher voltage to work?
• The quality of the copper and zinc can be problematic. Pennies are rarely pure copper. Try substituting a length of 14 gauge copper wire (common house wire). Experiment with different lengths and configurations of electrodes. Other sources of zinc and copper may be found in the plumbing department of a hardware store.

Discovery Questions

Beginning the experiment, during the experiment, after the experiment, how it works.

Electrochemical cells, also called batteries, require three things—two electrodes and one electrolyte. One of the electrodes has to have a stronger desire for electrons than the other—in chemistry we say that it has a higher electronegativity . The electrode that wants the electrons more is called the cathode , and the one that gives up electrons is electropositive and is called the anode .

Copper likes having electrons more than zinc so it’s more electronegative and is the cathode, leaving zinc to be the anode. An electrolyte is a solution that conducts electricity. The lemon provides citric acid, and acids contain ions which conduct electricity, making the lemon our electrolyte .

When zinc is exposed to the acid in the lemon juice, the acid oxidizes—or removes electrons from the zinc. The resulting positively charged zinc ions move into the lemon juice, and the resulting electrons collect in the zinc metal. They then rush across the wire into the copper which wants electrons more than zinc. Those electrons, now in the copper, pull a couple of protons or hydrogen ions out of the acid and reduce them, adding electrons, which creates hydrogen gas. If we could see inside the lemon, we might be able to see very very tiny bubbles of hydrogen gas forming on the copper electrode. In summary, the electricity is not coming from the lemon by itself, but from the chemical reaction resulting from the differences in electronegativities between zinc and copper.

Source: Dr. Christopher Gorski and Jenelle Fortunato, Penn State College of Engineering

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How do you get electricity from a lemon?

You have probably used batteries as a power source before – like in your flashlight. In this experiment, you can build a very simple battery yourself. Can you generate enough electricity to make headphones crackle?

Before you get started

If you are experimenting at home: 1. Let your parents know and discuss the experiments with them beforehand. 2. Do not eat or drink at your workspace.  3. Wash your hands thoroughly before and after the experiment.  4. Be careful and cautious with the materials. 

3. Making current audible

Now insert the plug of a headphone between the cable and the paper clip. You cannot see whether a small current is flowing, but you can make the current flow audible. Put the headphones in your ears and listen carefully: Does it crackle? Can other fruits also conduct electricity? Try it out!

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Citrus limon (Lemon) Phenomenon—A Review of the Chemistry, Pharmacological Properties, Applications in the Modern Pharmaceutical, Food, and Cosmetics Industries, and Biotechnological Studies

This review presents important botanical, chemical and pharmacological characteristics of Citrus limon (lemon)—a species with valuable pharmaceutical, cosmetic and culinary (healthy food) properties. A short description of the genus Citrus is followed by information on the chemical composition, metabolomic studies and biological activities of the main raw materials obtained from C. limon (fruit extract, juice, essential oil). The valuable biological activity of C. limon is determined by its high content of phenolic compounds, mainly flavonoids (e.g., diosmin, hesperidin, limocitrin) and phenolic acids (e.g., ferulic, synapic, p-hydroxybenzoic acids). The essential oil is rich in bioactive monoterpenoids such as D-limonene, β-pinene, γ-terpinene. Recently scientifically proven therapeutic activities of C. limon include anti-inflammatory, antimicrobial, anticancer and antiparasitic activities. The review pays particular attention, with references to published scientific research, to the use of C. limon in the food industry and cosmetology. It also addresses the safety of use and potential phototoxicity of the raw materials. Lastly, the review emphasizes the significance of biotechnological studies on C. limon .

1. Introduction

Citrus limon (L.) Burm. f. is a tree with evergreen leaves and yellow edible fruits from the family Rutaceae . In some languages, C. limon is known as lemon (English), Zitrone (German), le citron (French), limón (Spanish), and níngméng, 檸檬 (Chinese).

The main raw material of C. limon is the fruit, particularly the essential oil and juice obtained from it. The C. limon fruit stands out as having well-known nutritional properties, but it is worth remarking that its valuable biological activities are underestimated in modern phytotherapy and cosmetology [ 1 ].

C. limon fruit juice (lemon juice) has traditionally been used as a remedy for scurvy before the discovery of vitamin C [ 2 ]. This common use of C. limon , known since ancient times, has nowadays been supported by numerous scientific studies. Other uses for lemon juice, known from traditional medicine, include treatment of high blood pressure, the common cold, and irregular menstruation. Moreover, the essential oil of C. limon is a known remedy for coughs [ 3 , 4 , 5 ].

In Romanian traditional medicine, C. limon essential oil was administered on sugar for suppressing coughs [ 3 ]. Aside from being rich in vitamin C, which assists in warding off infections, the juice is traditionally used to treat scurvy, sore throats, fevers, rheumatism, high blood pressure, and chest pain [ 6 ].

In Trinidad, a mixture of lemon juice with alcohol or coconut oil has been used to treat fever, coughs in the common cold, and high blood pressure. Moreover, the juice or grated skin, mixed with molasses, has been used to remove excess water from the body, and the juice mixed with olive oil has been administered for womb infection and kidney stones [ 4 ]. According to Indian traditional medicine, C. limon juice can induce menstruation; the recommended dose for this is two teaspoons consumed twice a day [ 5 ].

Currently, valuable scientific publications focus on the ever wider pharmacological actions of C. limon fruit extract, juice and essential oil. They include studies of, for example, antibacterial, antifungal, anti-inflammatory, anticancer, hepatoregenerating and cardioprotective activities [ 7 , 8 , 9 , 10 , 11 ].

The pharmacological potential of C. limon is determined by its rich chemical composition. The most important group of secondary metabolites in the fruit includes flavonoids and also other compounds, such as phenolic acids, coumarins, carboxylic acids, aminoacids and vitamins. The main compounds of essential oil are monoterpenoids, especially D-limonene. These valuable chemical components are the reason for the important position of C. limon in the food and cosmetics industries [ 12 , 13 , 14 ].

The aim of this overview is a systematic review of scientific works and in-depth analyses of the latest investigations and promotions related to C. limon as a valuable plant species, important in pharmacy, cosmetology and the food industry. Additionally, relevant biotechnological investigations are presented.

2. The Genus Citrus

The genus Citrus is one of the most important taxonomic subunits of the family Rutaceae . Fruits produced by the species belonging to this genus are called ‘citrus’ in colloquial language, or citrus fruits. Citrus fruits are commonly known for their valuable nutritional, pharmaceutical and cosmetic properties. The genus Citrus includes evergreen plants, shrubs or trees (from 3 to 15 m tall). Their leaves are leathery, ovoid or elliptical in shape. Some of them have spikes. The flowers grow individually in leaf axils. Each flower has five petals, white or reddish. The fruit is a hesperidium berry. The species belonging to the genus Citrus occurs naturally in areas with a warm and mild climate, mainly in the Mediterranean region. They are usually sensitive to frost [ 2 ].

One of the best known and most used species of the genus Citrus is the lemon— Citrus limon (L.) Burm. f. (Latin synonyms: C. × limonia , C. limonum ). Other important species included in this taxonomic unit are: Citrus aurantium ssp. aurantium —bitter orange, Citrus sinensis —Chinese orange, Citrus reticulata —mandarin, Citrus paradise —grapefruit, Citrus bergamia —bergamot orange, Citrus medica —citron, and many others. A team of scientists from the University of California (Oakland, California, USA) [ 15 ] analyzed the origin of several species of the genus Citrus , including C. limon . They found that C. limon was a plant that had formed as a result of the combination of two species— C. aurantium and C. medica . In the studies of scientists from Southwest University of China (Chongqing, China), the metabolite profiles of C. limon, C. aurantium and C. medica were evaluated using gas chromatography–mass spectrometry (GC-MS) and the partial least squares discriminant analysis (PLS-DA) score plot [ 16 ]. They proved that C. limon has a smaller distance between C. aurantium and C. medica in comparison with other Citrus species. These studies demonstrated that C. limon was likely a hybrid of C. medica and C. aurantium, as previously suspected [ 16 ].

Botanical classification of the species of the genus Citrus is very difficult due to the frequent formation of hybrids and the introduction of numerous cultivars through cross-pollination. Hybrids are produced to obtain fruit with valuable organoleptic and industrial properties, including seedless fruit, high juiciness, and the required taste. For older varieties, hybrids and cultivars, the latest molecular techniques are often needed to identify them. C. limon , like many other prolific citrus species, gives rise to numerous varieties, cultivars and hybrids, which are presented in Table 1 and Table 2 acc. to [ 17 ].

C. limon cultivars.

Hybrids of C. limon .

One of the oldest preserved botanical sources describing species of the genus Citrus is the “Monograph on the Oranges of Wên-chou” (in Chinese: 記 嘉 桔 錄, “Citrus records of Ji Jia”) by Han Yanzhi from 1178 [ 18 , 19 ]. Other historical works describing the species bearing citrus fruits are “Nürnbergische Hesperides” from 1708 and “Traité du Citrus” from 1811. Historically, one of the best known classifications of citrus species is “Histoire Naturelle des Orangers” from 1818. The American botanist Walter Tennyson Swingle (1871–1952) had a particularly significant impact on the present-day taxonomy of the genus Citrus . He is the author of as many as 95 botanical names of species of the genus Citrus . Currently, the systematics of the species of the genus Citrus are based on studies of molecular markers and other DNA analysis technologies still provide new information [ 20 ].

3. Botanical Characteristics and Occurrence of C. limon

Citrus limon (L.) Burm. f. (lemon) is a tree reaching 2.5–3 m in height. It has evergreen lanceolate leaves. Bisexual flowers are white with a purple tinge at the edges of the petals. They are gathered in small clusters or occur individually, growing in leaf axils. The fruit is an elongated, oval, pointed green berry that turns yellow during ripening. Inside, the berry is filled with a juicy pulp divided into segments (like an orange). The C. limon pericarp is made of a thin, wax-covered exocarp, under which there is the outer part of the mesocarp, also known as flavedo. This part contains oil vesicles and carotenoid dyes. The inner part of the mesocarp, also known as the albedo, is made of a spongy, white parenchyma tissue. The endocarp, or ‘fruit flesh’, is divided into segments by the spongy, white tissue of the mesocarp [ 2 ].

The C. limon tree prefers sunny places. It grows on loamy, well-drained, moist soils with a wide pH range [ 1 , 2 ].

The location of the original natural habitat of C. limon is not accurately known [ 1 , 21 ]. However, C. limon is considered to be native to North-Western or North-Eastern India [ 2 , 17 ].

C. limon is mainly recognized as a cultivated species. It has been cultivated in southern Italy since the 3rd century AD, and in Iraq and Egypt since 700 AD. The Arabs introduced C. limon into Spain, where it has been cultivated since 1150. Marco Polo’s expeditions also brought C. limon to China in 1297. It was also one of the first new species that Christopher Columbus brought in the form of seeds to the North American continent in 1493. In the 19th century, worldwide commercial production of C. limon began in Florida and in California. Nowadays, the USA is the largest producer of C. limon . Italy, Spain, Argentina and Brazil also play a significant role [ 17 ].

4. C. limon Pharmacopoeial Monographs and Safety of Use

By cold-pressing the fresh outer parts of the C. limon pericarp (Lat. exocarpium ), an essential oil is obtained—the lemon oil (lat. Citrus limon aetheroleum , Limonis aetheroleum , Oleum Citri ). The oil is colourless or yellow, and has a characteristic, strong lemon scent [ 21 ]. It is considered a pharmacopoeial raw material. Its monographs, entitled ‘ Limonis aetheroleum ’, are present in the European Pharmacopoeia 9th [ 22 ], American Pharmacopoeia [ 23 ], and in the Ayurvedic Pharmacopoeia of India [ 24 ].

Another pharmacopoeial raw material obtained from C. limon is the outer part of the mesocarp —the flavedo . A monograph entitled ‘ Citrus limon flavedo ’ can be found in older editions of the French Pharmacopoeia, for example, in its 10th edition from 1998 [ 25 ].

The fresh fruit of C. limon is officially listed for use in phytotherapy and in homeopathy in Germany. According to the German Commission D Monographs for homeopathic medicines, C. limon fresh fruits can be used for treating gingival bleeding and debilitating diseases [ 26 ].

C. limon also has a positive recommendation in the European Commission’s Cosmetics Ingredients Database (CosIng Database) as a valuable plant for cosmetics’ production [ 27 ].

The European Food Safety Authority (EFSA) classified the pericarp, fruit, and leaves of C. limon as raw materials of plant origin, in which there is presence of naturally occurring ingredients that may pose a threat to human health when used in the production of food and dietary supplements. EFSA has remarked that the toxic substances in these raw materials are photosensitizing compounds belonging to the furanocoumarin group, including bergapten and oxypeucedanin ( Figure 1 ) [ 28 ].

Chemical structure of selected linear furanocoumarins, determining the photosensitizing effect of C. limon.

In the American Food and Drug Administration (FDA) list, C. limon essential oil and extracts are classified as safe products [ 29 ].

5. Chemical Composition of C. limon

The chemical composition of C. limon fruit is well known. It has not only been determined for the whole fruit but also separately for the pericarp, juice, pomace, and essential oil. The compositions of the leaves and the fatty oil extracted from C. limon seeds are also known. Due to the large number of C. limon varieties, cultivars and hybrids, various research centres undertake the task of analyzing the chemical composition of the raw materials obtained from them.

The most important group of bioactive compounds in both C. limon fruit and its juice, determining their biological activity, are flavonoids such as: flavonones—eriodictyol, hesperidin, hesperetin, naringin; flavones—apigenin, diosmin; flavonols—quercetin; and their derivatives ( Figure 2 ). In the whole fruit, other flavonoids are additionally detected: flavonols—limocitrin ( Figure 2 ) and spinacetin, and flavones—orientin and vitexin ( Table 3 and Table 4 ). Some flavonoids, such as neohesperidin, naringin and hesperidin ( Figure 2 ), are characteristic for C. limon fruit. In comparison to another Citrus species, C. limon has the highest content of eriocitrin ( Figure 2 ) [ 30 ].

Chemical structure of flavonoids characteristic of C. limon.

Composition of C. limon fruits extracts.

Composition of C. limon juice.

Phenolic acids are another important group of compounds found both in the juice and fruit. There are mainly two such compounds in the juice—ferulic acid and synapic acid, and their derivatives. In contrast, the presence of p-hydroxybenzoic acid has been confirmed in the fruit. In the fruit, there are also coumarin compounds, carboxylic acids, carbohydrates, as well as amino acids, a complex of B vitamins, and, importantly, vitamin C (ascorbic acid) ( Table 3 and Table 4 ) [ 1 , 12 , 13 , 31 , 32 , 33 , 34 , 35 , 36 ].

Another interesting group of compounds that are found in C. limon fruits are limonoids. Limonoids are highly oxidized secondary metabolites with polycyclic triterpenoid backbones. They mainly occur in citrus fruits, including lemons, in which they are found mainly in the seeds, pulp, and peel. There are predominantly two such compounds in C. limon fruits—limonin and nomilin ( Figure 3 ) [ 37 ]. Studies have shown that the concentrations of the compounds of this group are dependent on fruit growth and maturation stages. Young citrus fruits contain the highest amounts of these compounds, compared to ripe ones [ 38 ].

Chemical structure of limonoids characteristic of C. limon.

Analysis of macroelements in C. limon fruit showed the presence in pulp and peel of: calcium (Ca), magnesium (Mg), phosphorus (P), potassium (K) and sodium (Na) [ 36 ].

In C. limon seed oil, the main ingredients are fatty acids, such as arachidonic acid, behenic acid and linoleic acid, and also tocopherols and carotenoids ( Table 5 ) [ 33 , 35 ]. The latest studies showed that C. limon fruit pulp oil contains more fatty acids compared to other Citrus species, such as C. aurantium , C. reticulata and C. sinensis. The following fatty acids have been identified in C. limon pulp oil: behenic acid, erucic acid, gondoic acid, lauric acid, linoleic acid, α-linolenic acid, margaric acid, palmitic acid, palmitoleic acid, pentadecanoic acid, and stearic acid [ 39 ].

Composition of oil from C. limon seeds.

The main components of the C. limon essential oil are monoterpenoids. Among them, quantitatively dominant in the essential oil obtained from pericarp are: limonene (69.9%), β-pinene (11.2%), γ-terpinene (8.21%), ( Figure 4 ), sabinene (3.9%), myrcene (3.1%), geranial (E-citral, 2.9%), neral (Z-citral, 1.5%), linalool (1.41%). In addition to terpenoids, the essential oil also contains linear furanocoumarins (psoralens) and polymethoxylated flavones ( Table 6 ) [ 14 , 40 , 41 ].

Chemical structure of selected terpenoids characteristic of C. limon essential oil.

The chemical composition of the essential oil of the C. limon pericarp and leaf.

The essential oil of the C. limon leaf differs in composition from oil obtained from pericarp. Its main compounds include: limonene (31.5%), sabinene (15.9%), citronellal (11.6%), linalool (4.6%), neral (4.5%), geranial (4.5%), (E)-β-ocimene (3.9%), myrcene (2.9%), citronellol (2.3%), β-caryophyllene (1.7%), terpne-4-ol (1.4%), geraniol (1.3%) and α-pinene (1.2%) ( Table 6 ) [ 14 , 16 , 40 , 41 , 42 , 43 ].

6. Metabolomic Profile Studies

The team of Mucci et al. [ 35 ] investigated the metabolic profile of different parts of C. limon fruit. Flavedo, albedo, pulp, oil glands, and the seeds of lemon fruit and citron were studied through high resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy. The analyses were made directly on intact tissues without any physicochemical manipulation. In C. limon flavedo were detected: terpenoids (limonene, β-pinene and γ-terpinene), aminoacids (asparagine, arginine, glutamine, proline), organic acids (malic acid and quinic acid), osmolites (stachydrine), and fatty acid chains and sugars (glucose, fructose, β-fructofuranose, myoinositol, scylloinositol and sucrose) ( Table 3 ). The albedo of C. limon fruit showed the presence of low signals from: aminoacids (alanine, threonine, valine, glutamine), sugars (glucose, sucrose, β-fructofuranose, myoinosytol, scylloinositol and β-fructopyranose), and osmolites (stachydrine, β-hydroxybutyrate, ethanol) ( Table 3 ). In albedo, clear signals from flavonoids were detected, such as hesperidin and rutoside, that have been identified also by high performance liquid chromatography (HPLC) analyses. Oil glands’ HR-MAS NMR composition analysis showed the presence of terpenoids (limonene, γ-terpinene, β-pinene, α-pinene, geranial, neral, citronellal, myrcene, sabinene, α-thujene, nerol and geraniol esters) and sugars (glucose, sucrose, β-fructofuranose and β-fructopyranose). The analysis of C. limon pulp showed the presence of aminoacids (asparagine, proline, alanine, γ-aminobutyric acid (GABA), glutamine, threonine and valine), organic acids (citric acid and malic acid), sugars (glucose, sucrose, β-fructofuranose, β-fructopyranose, myoinosytol and scylloinosytol) and osmolites (stachydrine, ethanol and methanol) ( Table 3 ). HR-MAS NMR seeds analysis indicated that their composition is dominated by triglyceride signals (linoleic acid, linolenic acid and their derivatives), sugars (glucose and sucrose), osmolites (stachydrine) and trigonelline [ 35 ].

In another metabolomic study, the peel extracts of ripened C. limon fruit was characterized as containing nonfluorescent chlorophyll catabolites (NCCs) and dioxobilane-type nonfluorescent chlorophyll catabolite (DNCC) [ 44 ]. In the peels of C. limon fruit, four chlorophyll catabolites were detected: Cl-NCC1, Cl-NCC2, Cl-NCC3 and Cl-NCC4 [ 44 ].

The metabolomic profile of C. limon leaf was investigated by Asai et al. [ 45 ]. The studies showed that C. limon leaves contain 26 different organic acids and their derivatives (aconitic acid, 2-aminobutyric acid, 4-aminobutyric acid, ascorbic acid, benzoic acid, citramalic acid, citric acid, p-coumaric acid, ferulic acid, fumaric acid, glucaric acid, glycolic acid, 3-hydroxybutyric acid, 2-isopropylmalic acid, malic acid, malonic acid, 3-methylglutaric acid, oxamic acid, D-3-phenyllacetic acid, pipecolic acid, pyruvic acid, quinic acid, shikimic acid, succinic acid, threonic acid, urocanic acid), 21 aminoacids (alanine, γ-aminobutyric acid, anthranilic acid, asparagine, aspartic acid, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, pyroglutamic acid, serine, threonine, tryptophan, tyrosine, valine), and 13 sugars and sugar alcohols (arabinose, fructose, galactose, glucose, glycerol, inositol, lyxose, maltose, rhamnose, ribose, sorbose, sucrose, xylitol). Additionally, studied leaves have been exposed to stress conditions (leaves were placed in such a way that the edge of the petiole was in contact with the bottom of a glass bottle, soaked with 0.2 mM jasmonic acid and salicylic acid aqueous solutions, and incubated at 25 °C for 24 h). The content of aminoacids, such as, tyrosine, tryptophan, phenylalanine, valine, leucine, isoleucine, lysine, methionine, threonine, histidine, and γ-aminobutyric acid, was increased after this stress treatment [ 45 ].

According to Mehl et al. [ 46 ], the identification of volatile and non-volatile metabolites in C. limon essential oil is dependent on geographic origin and the analytical methods used. To evaluate the potential of volatile and non-volatile fractions for classification purposes, volatile compounds of cold-pressed lemon oils were analyzed, using modern methods like gas chromatography-flame ionization detector-mass spectrometer (GC-FID/MS) and fourier transform mid-infrared spectroscopy (FT-MIR), while the non-volatile residues were studied using FT-MIR with proton nuclear magnetic resonance ( 1 H-NMR) and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-TOF-MS). The studies lead to very good differentiation and classification of samples regarding their geographic origin and extraction process modalities. The essential oil from the Italian-originated C. limon fruit was enriched in α-thujene, α-pinene, α-terpinene, sesquiterpenoids (i.e., β-caryophyllene) and furocoumarins (i.e., bergamottin). The essential oil from Spanish and Argentinian C. limon fruit was characterized by significant terpene contents, such as limonene, but differed in imperatorin, and byakangelicol contents. The studies showed that essential oil from Spanish C. limon fruit contained more camphor and 4-terpineol, while Argentinian C. limon fruit contained more sabinene and cis-sabinene hydrate [ 46 ].

The studies performed by Jing et al. [ 16 ] focused on the identification of components in the essential oil of different Citrus species, including C. limon . In general, most of the studied essential oil components were identified as monoterpenoids. The major monoterpenes in C. limon essential oil were: limonene (70.37%), p-mentha-3,8-diene (18.00%), myrcene (4.40%), α-pinene (3.24%), α-thujene (1.05%) and terpinolene (0.90%) ( Table 6 ). Other monoterpenoids, which were identified as characteristic of C. limon, were: sabinene (0.28%), α-terpinene (0.22%), trans-muurola-4(14), 5-diene (0.18%), eucalyptol (0.12%), octanol acetate (0.03%), β-curcumene (0.03%), zonarene (0.03%), 7-epi-sesquithujene (0.02%), citronellyl acetate (0.02%), α-farnesene (0.01%) ( Table 6 ). The shown metabolite-based profiling model can be used to clearly discriminate the basic Citrus species. Limonene, α-pinene, sabinene and α-terpinene were the major characteristic components of the analyzed metabolomes of Citrus genotypes that contributed to their taxonomy [ 16 ].

Studies performed by Masson et al. [ 43 ] deal with furanocoumarin’s and coumarin’s metabolomic profile in essential oil from C. limon fruit peel. C. limon essential oil contained large amounts of both furanocoumarins and coumarins compared to another tested Citrus essential oils. In C. limon essential oil, 13 furanocoumarins were detected (bergamottin, bergapten, byakangelicol, byakangelicin, epoxybergamottin, 8-geranyloxypsoralen, heraclenin, imperatorin, isoimperatorin, isopimpinellin, oxypeucedanin, oxypeucedanin hydrate, phellopterin) and two coumarins (citropten and herniarin) ( Table 6 ) [ 43 ].

7. Biological Activity of C. limon Raw Materials

7.1. anticancer activity.

C. limon nanovesicles have been isolated from the fruit juice using the ultracentrifugation method and purification on a 30% sucrose gradient, using an in vitro approach. The study showed that isolated nanovesicles (20 µg/mL) inhibited cancer cell proliferation in different tumour cell lines, by activating a TRAIL-mediated apoptotic cell death. Furthermore, C. limon nanovesicles suppress chronic myeloid leukemia (CML) tumour growth in vivo by specifically reaching the tumour site and by activating TRAIL-mediated apoptotic cell processes ( Table 7 ) [ 47 ].

Biological activity of C. limon fruit extracts confirmed by scientific research.

Another study has shown that an 80:20 methanol:water extract from lemon seeds induces apoptosis in human breast adenocarcinoma (MCF-7) cells, leading to the inhibition of proliferation. This extract showed the highest (29.1%) inhibition of MCF-7 cells in an MTT assay (Cell Proliferation Kit), compared to ethyl acetate, acetone and methanol extracts. The results suggest that aglycones and glycosides of the limonoids and flavonoids present in the 80:20 methanol:water extract may potentially serve as a chemopreventive agent for breast cancer ( Table 7 ) [ 9 ].

7.2. Antioxidant Activity

It has been shown that the antioxidant activity of the flavonoids from C. limon —hesperidin and hesperetin—was not only limited to their radical scavenging activity but also augmented the antioxidant cellular defences via the ERK/Nrf2 signalling pathway ( Table 7 ) [ 8 ].

In addition, vitamin C prevents the formation of free radicals and protects DNA from mutations. Studies have also shown a reduction in lipid peroxidation in seizures and status epilepticus was induced by pilocarpine in adult rats [ 48 ].

7.3. Anti-Inflammatory Activity

Various in vitro and in vivo studies have been conducted to evaluate hesperidin metabolites, or their synthetic derivatives, at their effectiveness in reducing inflammatory targets including NF-κB, iNOS, and COX-2, and the markers of chronic inflammation ( Table 7 ) [ 8 ].

The essential oil from C. limon (30 or 10 mg/kg p.o .) exhibited anti-inflammatory effects in mice under formalin test by reducing cell migration, cytokine production and protein extravasation induced by carrageenan. These effects were also obtained with similar amounts of pure D-limonene. The anti-inflammatory effect of C. limon essential oil is probably due to the high concentration of D-limonene ( Table 8 ) [ 49 ].

Biological activity of C. limon essential oil confirmed by scientific research.

Studies by Mahmoud et al. [ 50 ] have shown the protective effects of limonin on experimentally induced hepatic ischemia reperfusion (I/R) injury in rats. The mechanism of these hepatoprotective effects was related to the antioxidant and anti-inflammatory potential of limonin mediated by the down-regulation of the TLR-signaling pathway [ 50 ].

In studies with the essential oil administered at a dose of 10 mg/kg p.o. , D-limonene induced a significant reduction in intestinal inflammatory scores, comparable to that induced by ibuprofen. The studies documented that D-limonene-fed rats had significantly lowered serum concentrations of TNF-α compared to untreated TNBS-colitis rats. The anti-inflammatory effect of D-limonene also involved the inhibition of TNFα-induced NF-κB translocation in fibroblast cultures. The application of D-limonene in colonic HT-29/B6 cell monolayers increased epithelial resistance. The study found evidence that IL-6 markedly decreased during dietary supplementation with D-limonene [ 51 ]. Another study showed that the oil moderately inhibited soybean 5-lipoxygenase (5-LOX) with an IC 50 value of 32.05 μg/mL ( Table 8 ) [ 52 ].

7.4. Antimicrobial Activity

Acetone extracts from C. limon fruits have shown inhibitory activity against the Gram-positive bacteria Enterococcus faecalis (MIC 0.01 mg/mL) and Bacillus subtilis (MIC 0.01 mg/mL), and the Gram-negative Salmonella typhimurium (MIC 0.01 mg/mL) and Shigella sonnei (MIC 0.01 mg/mL) ( Table 7 ) [ 7 ].

Moreover, under another study, C. limon essential oil showed antibacterial activity against Gram-positive bacteria ( Bacillus subtilis (MIC 2 mg/mL), Staphylococcus capitis (MIC 4 mg/mL), Micrococcus luteus (MIC 4 mg/mL)), and Gram-negative ( Pseudomonas fluorescens (MIC 4 mg/mL), Escherichia coli (100% inhibition)) ( Table 8 ) [ 52 , 53 ].

The C. limon essential oil exhibits inhibitory activity against Staphylococcus mutans (MIC 4.5 mg/mL) and effectively reduced the adherence of S. mutans on a glass surface, with adherence inhibition rates (AIR) from 98.3% to 100%, and on a saliva-coated enamel surface, for which the AIRs were from 54.8% to 79.2%. It effectively reduced the activity of glucosyltransferase (Gtf) and the transcription of Gtf in a dose-dependent manner ( Table 8 ) [ 54 ].

Ethanol and acetone extracts from fruits of C. limon were active against Candida glabrata (MIC 0.02 mg/mL) ( Table 7 ) [ 7 ]. On the other hand, C. limon essential oil ingredients, such as D-limonene, β-pinene and citral, have shown inhibitory activity against Aspergillus niger (MIC 90 µL/mL at 70 °C), Saccharomyces cerevisiae (MIC 4 mg/mL) and Candida parapsilosis (MIC 8 mg/mL) ( Table 8 ) [ 52 , 55 ]. Another study confirmed that C. limon essential oil promoted a 100% reduction in the growth of C. albicans [ 56 ].

Moreover, other studies have shown that C. limon essential oil at a concentration of 0.05% inhibits Herpes simplex replication to the extent of 33.3% ( Table 8 ) [ 57 ].

7.5. Antiparasitic Effect

The effect of C. limon essential oil on Sarcoptes scabiei var. cuniculi has been evaluated in vitro and in vivo. The infected parts of rabbits were treated topically once a week for four successive weeks. In vitro application results showed that C. limon essential oil (10% and 20%, diluted in water) caused mortality in 100% of mites after 24 h post-application. In vivo application of 20% lemon oil on naturally infected rabbits showed complete recovery from clinical signs and absence of mites in microscopic examination from the second week of treatment ( Table 8 ) [ 58 ].

7.6. Anti-Allergic Effect

Aqueous extracts from the peel of C. limon fruits have been used to investigate their effects on the release of histamine from rat peritoneal exudate cells (PECs). The extracts inhibited the release of histamine from rat PECs induced by the calcium ionophore A23187. Heating the extracts at 100 °C for 10 min. enhanced the inhibition of histamine release. Histamine release was inhibited to the extent of 80%. The extracts potentially suppressed inflammation in mice cavity, like indometacin, a well-known anti-inflammatory drug ( Table 7 ) [ 59 ].

7.7. Hepatoregenerating Effect

An ethanolic extract of C. limon fruits has been evaluated for its effects on experimental liver damage induced by carbon tetrachloride (CCl 4 ), and the ethyl acetate soluble fraction of the extract has been evaluated for its effect on the HepG2 cell line (human liver cancer cell line). The ethanolic extract (150 mg/mL) normalized the levels of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), alkaline phosphatase (ALP), and total direct bilirubin, which had been altered due to CCl 4 intoxication in rats. After treatment with the extract, the level of malondialdehyde in the liver tissue was significantly reduced, hence the lipid peroxidation, and raised the level of the antioxidant enzymes superoxide dismutase and catalase. It improved the reduced glutathione levels in the treated rats in comparison with CCl 4 -intoxicated rats. The effect seen was dose dependent, and the effect of the highest dose was almost equal to the standard—silymarin. In an investigation carried out on a human liver-derived HepG2 cell line, a significant reduction in cell viability was observed in cells exposed to CCl 4 ( Table 7 ) [ 10 ].

Studies with C. limon essential oil have also shown the stimulation of liver detoxification by the activation of cytochrome P 450 and liver enzymes (glutathione S-transferase) in chronic liver poisoning ( Table 8 ) [ 21 ].

7.8. Antidiabetic Effect

Ethanol extracts from C. limon peel were administered orally at a dose of 400 mg/kg daily for 12 days to diabetic rats in which diabetes had been induced by the use of streptozotocin. The study showed a reduction in blood glucose, a reduction in wound healing time, and an increase in tissue growth rate, collagen synthesis, and protein and hydroxyproline levels ( Table 7 ) [ 60 ].

Another study evaluated the antidiabetic effect of D-limonene in streptozotocin-induced diabetic rats. D-limonene was administered orally at doses of 50, 100 and 200 mg/kg body weight, and glibenclamide at a dose of 600 µg/kg body weight, daily for 45 days. The administration of D-limonene for 45 days gradually decreased the blood glucose level, and the maximum effect was observed at a dose of 100 mg/kg body weight. The activities of gluconeogenic enzymes, such as glucose 6-phosphatase and fructose 1,6-bisphosphatase, were increased, and the activity of the glycolytic enzyme, glucokinase, was decreased, along with liver glycogen, in the diabetic rats. The effect of D-limonene was more pronounced at the dose of 100 mg/kg body weight than at the two smaller doses. The antidiabetic effect of D-limonene was comparable with that of glibenclamide ( Table 8 ) [ 61 ].

7.9. Anti-Obesity Activity

In a study, lemon juice was used in a low-calorie diet (‘lemon detox diet’). The diet consisted of 2 L of lemon detox juice containing 140 g ‘Neera’ syrup, 140 g lemon juice, and 2 L water per day. The study showed that C. limon juice caused a reduction in serum high-sensitive C-reactive protein (hs-CRP) in comparison with the placebo and normal diet group. Haemoglobin and haematocrit levels remained stable in the group on the lemon detox diet, while they decreased in the placebo and normal diet groups ( Table 7 ) [ 62 ].

Studies have shown that D-limonene is beneficial to people with dyslipidaemia and hyperglycaemia. D-limonene at a dose of 400 mg/kg per day for 30 days promotes in male rats a decrease in LDL-cholesterol, prevents the accumulation of lipids, and affects the blood sugar level. Its antioxidant action enhances these effects. Dietary supplementation with D-limonene would restore pathological alteration of the liver and pancreas. It could help in the prevention of obesity ( Table 8 ) [ 21 ].

7.10. Effects on the Digestive System

Studies have shown that D-limonene increases gastric motility and causes a reduction in nausea, neutralization of stomach acids, and relief of gastric reflux ( Table 8 ) [ 21 ].

7.11. Effects on the Cardiovascular System

A study has indicated that daily intake of C. limon juice has a beneficial effect on blood pressure. The study was conducted on 100 middle-aged women in an island area nearby Hiroshima. Instances of lemon juice ingestion and the number of steps walked had been recorded for five months. The results indicated that daily lemon juice intake and walking were effective in reducing high blood pressure because both showed significant negative correlations with systolic blood pressure ( Table 7 ) [ 63 ].

In vitro and in vivo studies have confirmed that C. limon juice (0.4 mL/kg) has a significant impact on blood pressure and on coagulation and anticoagulation factors in rabbits. In vitro tests revealed a highly significant increase in thrombin time and activated partial thromboplastin time by C. limon , whereas fibrinogen concentration was significantly reduced in comparison with the control; prothrombin time, however, was not affected significantly. Significant changes were observed in haematological parameters, such as amounts of erythrocytes and haemoglobin and mean corpuscular haemoglobin concentrations, in in vivo testing of C. limon . Bleeding time and thrombin time were significantly prolonged, and there was an increase in protein C and thrombin–antithrombin complex levels ( Table 7 ) [ 11 ].

7.12. Influence on the Nervous System

The influence of C. limon juice on the memory of mice has been investigated using Harvard Panlab Passive Avoidance response apparatus, controlled through the LE2708 Programmer. Passive Avoidance is a fear-motivated test used to assess the short- or long-term memory of small animals, which measures the latency in entering a black compartment. Animals that were fed C. limon juice (0.2, 0.4 and 0.6 mL/kg) showed, in comparison with the control, a highly significant or a significant increase in latency before entering a black compartment after 3 and 24 h, respectively ( Table 7 ) [ 64 ].

Studies have also shown that the main compound of C. limon essential oil—D-limonene—in concentrations of 0.5% and 1.0%, administered to mice by inhalation, has a significant calming and anxiolytic effect by activating serotonin and dopamine receptors. In addition, D-limonene has an inhibitory effect on pain receptors, similar to that of indomethacin and hyoscine ( Table 8 ) [ 65 ].

7.13. Influence on Skeletal System

Studies have shown the potential use of nomilin for the inhibition of osteoclastogenesis in vitro. Cell viability of the mouse RAW264.7 macrophage cell line and mouse primary bone-marrow-derived macrophages (BMMs) with the Cell Counting Kit (Dojindo Laboratories, Kumamoto, Japan) was measured. Nomilin caused significantly decreased TRAP-positive multinucleated cell numbers (a measure of osteoclast cell numbers) when compared with the control. Moreover, the non-toxic concentrations of the compound decreased bone resorption activity and down regulated osteoclast-specific genes (NFATc1 and TRAP mRNA levels), coupled with suppression of the MAPK signaling pathway. Studies have shown the therapeutic potential of nomilin for the prevention of bone metabolic diseases such as osteoporosis [ 66 ].

7.14. C. limon as Corrigent in Pharmacy

In addition to the very important uses mentioned above, the oil is used in pharmacy and cosmetic formulations as a flavour and aroma corrigent, as well as a natural preservative, due to its confirmed antibacterial and fungistatic effects [ 21 ].

8. C. limon in the Food Industry

Due to the rich chemical composition of C. limon fruit and other lemon-derived raw materials, they have applications in the food industry and in food processing. The lemon fruit is used mainly as a fresh fruit, but it is also processed to make juices, jams, jellies, molasses, etc. [ 41 ]. Fresh lemon fruit can be kept for several months, maintaining their levels of juice, vitamins, minerals, fibre, and carbohydrates. The vitamin C (ascorbic acid) content in lemon fruits and juices decreases during storage and industrial processing. The factors lowering this content are: oxygen, heat, light, time, storage temperature and storage duration. To prevent the reduction in the ascorbic acid levels and antioxidant capacity of both the lemon fruit and lemon juice, they should be kept at 0–5 °C and protected from water loss by proper packaging, with high relative humidity during distribution. Under such conditions, lemon products show a good retention of vitamin C and antioxidant capacity [ 41 , 74 ].

C. limon peel is rich in pectin, which is used in a wide range of food industrial processes as a gelling agent, including the production of jams and jellies, and as thickener, texturizer, emulsifier and stabilizer in dairy products. Due to its jellifying properties, the pectin is also used in pharmaceutical, dental and cosmetic formulations [ 75 ].

Lemon juice is used as an ingredient in beverages, particularly lemonade and soft drinks, and in other foods, such as salad dressings, sauces, and baked products. Lemon juice is a natural flavouring and preservative, and it is also used to add an acidic, or sour, taste to foods and soft drinks [ 41 , 76 ].

C. limon is the most suitable, being free from pesticide residues, raw material for enhancing the flavour of liqueurs, e.g., “limoncello”, the traditional liqueur of Sicily. It is made by the maceration of lemon peel in ethanol, water and sugar [ 41 , 76 ].

Currently, the essential oil from lemon, i.e., pure isolated linalol and citral, are used mainly as a flavouring and natural preservative due to their functional properties (antimicrobial, antifungal, etc.) [ 52 , 53 ]. In particular, they are often used to extend the short shelf-life of seafood products and in the production of some types of cheese because they significantly reduces populations of microorganisms, especially those from the family Enterobacteriaceae [ 41 , 76 ].

9. Cosmetological Applications

C. limon fruit extracts and essential oil, as well as the active compounds isolated from these raw materials, have become the object of numerous scientific studies aimed at proving the possibility of their use in cosmetology. Lemon-derived products have long been credited with having a positive effect on acne-prone skin that is easily affected by sunburn or mycosis. In this regard, traditional uses of this raw materials are known in various parts of the world. In Tanzania, the fruit juice of C. limon is mixed with egg albumin, honey and cucumber, and applied to the skin every day at night to smooth the facial skin and treat acne [ 77 ]. Juice from freshly squeezed fruit of C. limon mixed with olive oil is used as a natural remedy for the treatment of hair and scalp disorders in the West Bank in Palestine [ 78 ]. Currently, knowledge of the cosmetic activity of C. limon is constantly expanding.

C. limon essential oil shows antibiotic and flavouring properties, and for this reason it is used in formulations of shampoos, toothpaste, disinfectants, topical ointments and other cosmetics [ 41 ].

Scientific studies have shown a significant antioxidant effect of C. limon fruit extracts, which is the reason they are recommended for use in anti-ageing cosmetics [ 8 , 48 ]. The use of different carriers for C. limon extracts (e.g., hyalurosomes, glycerosomes) in cosmetics production technology contributes to an even greater inhibition of oxidative stress in skin-building structures, including keratinocytes and fibroblasts ( Table 9 ) [ 79 ]. In addition, vitamin C from C. limon is used as an ingredient in specialized dermocosmetics. Its external use increases collagen production, which makes the skin smoother and more tense. It is used in anti-aging products, to reduce shallow wrinkles, and as a synergistic antioxidant in combination with vitamin E [ 48 ].

Biological activity of C. limon fruit extracts, essential oil and its ingredients compounds significant from the cosmetics point of view, confirmed by scientific research.

The ingredients of C. limon essential oil (including citral, β-pinene, D-limonene), due to the inhibiting activity of tyrosinase and the inhibition of L-dihydroxyphenylalanine (L-DOPA) oxidation, have a depigmenting effect [ 80 ]. In addition, the essential oil has been proven to support the penetration of lipids as well as water-soluble vitamins. It can be used as a promoter of penetration of active substances through the skin [ 81 ]. Moreover, besides the direct effect on the skin, the essential oil can also be used as a natural preservative and as a corrigent in cosmetic products. Studies have confirmed its antibacterial and fungistatic effects ( Table 9 ) [ 7 , 52 , 53 ].

Furthermore, C. limon pericarp extracts, too, exhibit scientifically proven activity that helps to accelerate the regeneration of diabetic wounds. In addition, the essential oil derived from C. limon pericarp has shown anti-inflammatory, anti-allergic and slimming properties [ 49 , 59 , 60 , 62 ].

According to the CosIng Database (Cosmetic Ingredient Database), C. limon can be used in twenty-three forms. It can be used in cosmetics in the form of oils obtained from various organs, in the form of extracts, hydrolates, powdered parts of the plant, wax and juice [ 27 ]. The most common activity defined by CosIng for the raw material of this species is to keep the skin in good condition, to improve the odour of cosmetic products, and to mask the smell of other ingredients of cosmetic preparations [ 27 ]. The approved forms of raw materials and their potential effects, as well as their use as corrigents, presented in the CosIng Database, are summarized in Table 10 [ 27 ].

C. limon in cosmetic products according to CosIng.

C. limon essential oil has been used since the 18th century in the production of the famous ‘Eau de Cologne’. In aromatherapy, it is used to treat numerous diseases and lifestyle-related ailments: hypertension, neurosis, anxiety, varicose veins, arthritis, rheumatism and mental heaviness. It also alleviates symptoms characteristic of menopause. C. limon essential oil is also used in aromatherapy massages to relax muscles, and for calming down and deep relaxation [ 21 ].

C. limon fruit extracts and essential oil should not be used in high concentrations in baths or directly on the skin. Recent studies have shown that D-limonene contained in the oil has an allergenic and irritating effect on the skin. It may cause cross-allergy with balsam of Peru. After applying cosmetics containing C. limon oil, it is forbidden to expose the skin to sunlight . C. limon essential oil contains photosensitizing compounds belonging to the linear furanocoumarin group. The lemon pericarp contains: bergapten, phellopterin, 5- and 8-geranoxypsoralen, and the essential oil contains: bergapten, imperatorin, isopimpinellin, xanthotoxin, oxypeucedanin and psoralen [ 21 , 82 ].

The International Fragrance Association (IFRA) has issued restrictions on the use of C. limon essential oil. In preparations remaining on the skin, the concentration of that oil should not exceed 2%. In addition, C. limon essential oil should not be used in preparations remaining on skin exposed to UV rays. They should not contain more than 15 ppm of bergapten [ 83 ].

10. Plant Biotechnological Studies on C. limon

Plant biotechnology creates opportunities for the potential use of plant in vitro cultures in the pharmaceutical, cosmetics and food industries. In vitro cultures can be a good alternative to plants growing in vivo. Plant biotechnology enables control and optimization of the conditions for conducting in vitro cultures to increase the accumulation of active compounds. It facilitates, among other things, optimization of the culture medium, including the concentration of plant growth and development regulators, the use of elicitors (stressors), the selection of highly productive cell lines and genetic transformations. In vitro cultures can also be used in plant propagation (micro-propagation process) [ 84 ].

C. limon cultures in vitro have thus far been the subject of research concerned with the development of micropropagation protocols. They have focused on the selection of plant growth regulators (PGRs) that induced shoot and root production in in vitro cultures. In 2012, biotechnological research on the micropropagation of C. limon was performed by Goswami et al. [ 85 ] from SKN Rajasthan Agricultural University in India. Shoot cultures were propagated from plant nodes on a Murashige and Skoog (MS) medium [ 86 ] containing different types and concentrations of PGRs. The maximum number of shoots and shoot regenerations was observed at a low level of 6-benzyladenine (BA) −0.1 mg/L, or kinetin −0.5 mg/L. Shoot proliferiation was also observed in combinations of PGRs such as BA and 1-naphthaleneacetic acid in concentrations of 0.1 mg/L each. With an increase in BA concentration in MS medium, shoot proliferation decreased. Regenerated shoots showed root induction on MS basal medium or on MS medium containing 1.0 mg/L of indole-3-butyric acid.

Another biotechnological study on C. limon was carried out in the Department of Citriculture in Murcia (Spain) [ 87 ]. The researchers studied organogenesis and made histological characterization of mature nodal explants of two important cultivars of C. limon —‘Verna 51’ and ‘Fino 49’. The highest number of buds per regenerating explant was obtained on the MS medium in comparison with the Woody plant medium [ 88 ]. The presence of 1–3 mg/L BA, in combination with 1 mg/L of 1-gibberellic acid (GA) in the culture medium, was essential for the development of adventitious buds. The lowest extent of organogenesis was observed when BA was used in the medium without GA [ 87 ].

11. Conclusions

The presented review proves that C. limon is a very attractive object of different scientific studies. The C. limon fruit is a raw material that can be used in different forms, e.g., extracts, juice and essential oil. The rich chemical composition of this species determines a wide range of its biological activity and its being recommended for use in phytopharmacology. The studies have focused on the essential oil and its main active compound—D-limonene. Extracts from C. limon fruits are rich in flavonoids such as naringenin and hesperetin.

Current pharmacological studies have confirmed the health-promoting activities of C. limon , especially its anti-cancer and antioxidant properties. C. limon also finds increasing application in cosmetology and food production.

There has been some biotechnological research aimed at developing effective in vitro micropropagation protocols for C. limon .

Author Contributions

Conceptualization, A.S., H.E. and M.K.-S.; data curation, A.S. and M.K.-S.; writing—original draft preparation, A.S. and M.K.-S.; writing—review and editing, A.S., M.K.-S. and H.E.; supervision, A.S. and H.E. All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Conflicts of Interest

The authors declare no conflicts of interest.