Isolate Caffeine from tea leaves. Pharmacognosy Practical

 Experiment

Object: 

 Isolate Caffeine from tea leaves.

Reference:

1) Kokate C. K. Practical Pharmacognosy, Vallabh Prakashan; New Delhi;4th edition (1994), pg. 511

2) Kokate C. K. Practical Pharmacognosy, Vallabh Prakashan; New Delhi; 4th edition (1994), pg. 140. 

Requirements: 

 Vacuum distillation unit, Soxhlet extractor, Porcelain dish, Ethanol 

(95%), Sulphuric acid, Chloroform, Sodium hydroxide, Nitric acid, Ammo. hydroxide, 

Tea powder.

Theory :

Caffeine is a member of the class of compounds organic chemists called alkaloids. Alkaloids are nitrogencontaining basic compounds that are found in plants. 

They usually taste bitter and often are physiologically active in humans. The names of some of these compounds are familiar to you even if the structures aren’t: nicotine, morphine, strychnine, and cocaine. The role or roles these compounds play in the life of the plants in which they are found is not well understood. In some cases they may act as pesticides; nicotine is found in tobacco and has been sprayed onto other plants, in which it is not found, to function as an insecticide.

 The structure of caffeine is shown to the right. It can be considered to be constructed from the purine ring system, which is important biologically, being found in nucleic acids and elsewhere. Caffeine is found in a number of things ingested by people. The table to the right lists some of them. 

Caffeine acts as a stimulant. It stimulates the heart, respiration, the central nervous system, and is a diuretic. Its use can cause nervousness, insomnia and headaches. It is physically addictive.

 A person who drinks as few as 4 cups of coffee a day and who attempts to stop “cold turkey” may experience headache, insomnia, and possibly nausea as the result of withdrawal.

Procedure:

1. Extract 50 gms of powdered tea with 200 ml of ethanol for 6 hours in a soxhlet apparatus.

2. Transfer the extract to a porcelain dish containing 30 gms of magnesium oxide in 200 ml of water. Evaporate with frequent stirring on a steam bath.

3. Boil residue thrice with 100 ml of water, filter while hot on a Buchner funnel, add 30 ml of 10 % sulphuric acid to combined filtrate and then concentrate under vacuum to about one third of the original volume.

4. Filter the solution while hot and extract with a few ml of 1 % sodium hydroxide till the decolourization takes place. Add equal volume of water. Separate the chloroform layer. 

5. Treat chloroform extract with a few ml of 1% sodium hydroxide till the decolourization takes place. Add equal volume of water separate the chloroform layer.

6. Evaporate the chloroform extract and recrystalline the crude caffeine from a very small volume of hot water .

7. Calculate the % yield.

Result:

The % yield of caffeine was found to be_____%.

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method of Caffeine extraction form tea, 

laboratory method of caffeine extraction,

How caffeine is extracted from tea leaves,