Aim: To isolate caffeine from tea leaves.
- Vacuum distillation unit,
- Soxhlet Extractor,
- Porcelain dish,
- Sulphuric acid,
- Sodium hydroxide,
- Nitric acid,
- Ammonium hydroxide,
- Tea Leaves.
Caffeine is a methyl derivative of xanthine present in tea and coffee. Caffeine is used as a central nervous system stimulant and it is a less potent diuretic than theobromine.
Synonyms: Chai, Camellia, Thea
Biological Source: It contains the prepared leaves and leaf buds of plant Thea sinensis Linn, O.kuntze
- Odour: Characteristics
- Taste: Bitter
- Leaves: Dark green, lanceolate, or elliptical, blunt at the apex, base is tapering, margin, shortly serrate.
- Flowers: Solitary or in groups of 2 to 3 in the leaf axil and drooping.
- Rich source of Caffeine(1-3%)
- Theobromine and theophylline.
- Colour of leaves is due to gallotannic acid (15%).
- Extract 50g of powdered tea with 200ml of ethanol for 6 hours in Soxhlet apparatus.
- Transfer the extract to a porcelain dish containing 30g of magnesium oxide in 200ml of water. Evaporate with frequent stirring on a steam bath.
- Boil residue thrice with 100ml 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 1/3rd of the original volume. Filter the solution while hot & extract with five portions of 25ml of chloroform.
- Treat chloroform extract with a few ml of 1% NaOH till the decolorization takes place.
- Add equal volume of water separate the chloroform layer.
- Evaporate the chloroform extract and recrystallize the crude caffeine from a very small volume of hot water.
- The Yield is 1g approximately of silky needles of caffeine.