Extraction of Caffeine from Tea Leaves

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Extraction of Caffeine from Tealeaves
Perez, Albert Solomon K.*; Quiambao, Marie Angela C;.Pascua, Hanna Harriette R.; Patricio, Maria Roxanne DC.; 2-Chemistry, Department of Chemistry, College of Science
University of Santo Tomas
España St., 1015, Manila


Caffeine is soluble in both water and organic solvents, solid-liquid extraction and liquid-liquid extraction were used in the experimentation process. Caffeine was extracted using hot water, however, due to its medium polarity; it was further separated from water soluble compounds using a polar non-protic solvent, dichloromethane (CH2Cl2). Sublimation was then used for the purification of the targeted compound. Based from the data collected, 5.758g of tea leaves contains 3.96% caffeine. After the purification process, 0.2279g of caffeine was obtained from 0.4948g crude extract with 46.06% yield. Melting point determination was used to characterize the caffeine yielded. However, the melting point range of the caffeine collected (190°C -215 °C) was lower than the melting point of the accepted value (238 °C) which may be due to experimental errors committed in the extraction and washing process.

Tea has been consumed as a beverage for almost 2,000 years starting in China. It is the most widely consumed beverage after water [1].Their active participation in trade resulted in its introduction to Europe. The active component in tea is caffeine (C8H10N4O2). Caffeine belongs to an extensive class of compounds known as the alkaloids. Alkaloids are a diverse group of compounds that are found primarily in plants and contain basic nitrogen atom(s). The basic nature of these compounds makes them exists mostly as salts. Many alkaloids have profound effects on the nervous system and acts as a mild stimulant examples are other well-known alkaloids such as morphine, strychnine, quinine, ephedrine, and nicotine. Aside from being a mild stimulant, caffeine is one of the most promising organic compounds in medicine, in a study by Miura, T. et al., green tea extracts showed lowering in blood pressure of a mice with diabetes type 2 and thus a plausible treatment for diabetes[2]. However, caffeine may be associated with serious ventricular arrhythmias in susceptible people. Caffeine may increase beat-to-beat heart rate variability and also QT interval variability during rapid eye movement sleep[3].

Caffeine cannot be obtained directly; every pot of coffee or cup of tea involves solid/liquid extraction, the extraction of organic compounds from solid ground beans or leaves using hot water as the liquid. The lower molecular weight polar molecules such as caffeine dissolve in the hot water and are removed from the high molecular weight water-insoluble cellulose, protein, and lipid materials. Over 200compounds, some in only trace quantities are extracted from the solid into a cup of coffee or tea. Figure 1 shows the chemical structure of caffeine. [pic]

Figure1. Caffeine
While solid-liquid extraction is the most common technique used to brew beverages and isolate natural products, liquid/liquid extraction is a very common method used in the organic laboratory. Organic reactions often yield a number of by-products, some inorganic, some organic. Also, since they do not go to 100% completion, some starting material is also often present at the end of an organic reaction. Liquid-liquid extraction is often used as the initial step in the work-up of a reaction, before final purification of the product by recrystallization, distillation or sublimation.

Varying extracts from various plants have been used as teas, potions, medicines and poisons. However, these extracts can contain a mixture of many different chemicals, often only one or few are responsible for the activity of the extract. The objective of this experiment is to isolate, purify and characterize caffeine from tea leaves. Moreover, to calculate the percent yield of caffeine....
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