To isolate caffeine from Tea Leaves – Herbal Drugs Technology, Pharmacognosy

Aim: To isolate caffeine from tea leaves.

Requirements

  • Vacuum distillation unit,
  • Soxhlet Extractor,
  • Porcelain dish, 
  • Ethanol,
  • Sulphuric acid,
  • Chloroform,
  • Sodium hydroxide,
  • Nitric acid,
  • Ammonium hydroxide,
  • Tea Leaves.

Theory

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.

Tea Leaves

Synonyms: Chai, Camellia, Thea

Biological Source: It contains the prepared leaves and leaf buds of plant Thea sinensis Linn, O.kuntze

Family: Theaceae

Macroscopic Characteristic:

  • 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.

Chemical Constituents:

  • Rich source of Caffeine(1-3%)
  • Theobromine and theophylline.
  • Colour of leaves is due to gallotannic acid (15%).

Procedure

  1. Extract 50g of powdered tea with 200ml of ethanol for 6 hours in Soxhlet apparatus.
  2. Transfer the extract to a porcelain dish containing 30g of magnesium oxide in 200ml of water. Evaporate with frequent stirring on a steam bath.
  3. 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.
  4. Treat chloroform extract with a few ml of 1% NaOH till the decolorization takes place.
  5. Add equal volume of water separate the chloroform layer.
  6. Evaporate the chloroform extract and recrystallize the crude caffeine from a very small volume of hot water.
  7. The Yield is 1g approximately of silky needles of caffeine.

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