Caffeine is chemically 1,3,7-trimethylxanthine, a purine base, found in tea, cocoa, kola, guarana, etc. It is mainly isolated from tea leaves and coffee beans using the decaffeination process. This compound was discovered in 1821 by Robiquet in coffee and by Oudry in 1827, through the isolation of caffeine from tea leaves.Â
Here, we will see the methods of isolation of caffeine. Caffeine produces a white precipitate with tannic acid solution.
Murexide colour reaction
- Caffeine is taken in a petridish, and hydrochloric acid and potassium chlorate crystals are addedÂ
- This mixture is heated until dry
- This mixture, when exposed to vapours of dilute ammonia, a purple-coloured residue.Â
- When fixed alkali is added, this purple colour disappears.
Isolation of Caffeine
Depending on the source, there are different isolation methods for caffeine.
Boiling Water Method
From tea leaves, it is extracted using hot boiling water. This extract is treated with lead acetate to precipitate tannins. The filtrate is boiled with charcoal to remove any colouring matter. The decoloured extract is extracted with chloroform. The chloroform is allowed to evaporate to get white coloured caffeine.
Soxhlet Method
The Soxhlet extraction of tea leaves in ethanol gets caffeine in ethanol. It is then absorbed on magnesium oxide and again treated with 10% sulfuric acid. It is extracted with chloroform to obtain caffeine.
Leaching Method
Caffeine from coffee beans is extracted by leaching with water. Coffee beans are made into a coarse powder. This powder is treated with water at 75 degrees Celsius, which will get 90% of caffeine. It takes about half an hour to complete this process, and the ratio used is 9:1 for water and coffee.Â
Supercritical Fluid Extraction Method
The Supercritical Fluid Extraction method is the process used for the decaffeination of coffee. The medium, liquid carbon dioxide, used here is circulated through moist coffee and then through a second vessel containing an absorbing medium such as activated carbon, resin, or water. The absorbed caffeine is separated using chloroform.Â
Thin Layer Chromatography of Caffeine
- Dissolve 1 mg of caffeine in 1 ml of chloroform or methanol.
- Load the sample on a TLC plate.
- Elute it in ethyl acetate–methanol–acetic acid in the ratio of 80:10:10.Â
- The TLC plate is exposed to iodine vapour.
- Caffeine develops a spot at Rf value 0.41.
Uses of Caffeine
Caffeine is used in various industries for different purposes. It is widely used,
- In cosmetic ointments.
- As a coating for pills in the pharmaceutical industry.
- To prepare suppositories.
- As an emollient in cosmetics to make a moisturiser for hands and lips.
- As a diuretic.
- To reduce blood pressure as a blood dilator.
- As a nutritive agent in food.
- It may help lower the risk of developing Parkinson’s
- Stimulate the gallbladder to reduce gallstones.
- Reduces inflammation, treats migraine, and relieves asthma
References
- Shah, Biren N, Avinash Seth. (2010). Textbook of Pharmacognosy and Phytochemistry. Elsevier.
- Isolation & analytical technique of caffeine from different sources: A review. (2024). In Journal of Medicinal Plants Studies (Vols. 12–12, pp. 197–202). https://www.plantsjournal.com/archives/2024/vol12issue1/PartC/11-6-21-679.pdf
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