Synonym: Camellia thea.
Biological source: Tea contains prepared leaves and leaf buds of Thea sinensis Linn.
Family: Theaceae.
Geographical source: Tea is cultivated in India, Srilanka, Indonesia, China and Japan. In
India it is cultivated in North-Eastern India (mainly in Assam and Bengal).
Cultivation and Collection:
The tea is available in two forms:
1. Black tea
2. Green tea
Black tea is available from India and Srilanka whereas green tea is available from China and Japan. Black tea is obtained by fermentation of fresh tea leaves which further dried artificially.
Green tea is obtained by keeping tea leaves in copper vessel and then dried artificially.
Macroscopic Characters:
The cultivated tea is small evergreen shrub which is 1 to 1.5 meter in height. The wild plants are up to 6 meter in height. The leaves are dark green in colour, lanceolate, elliptical,
blunted at apex, serrate, hairy and glabrous in nature. Flowers are solitary in nature and generally in group of 2 to 3 leaf axils. It possesses characteristic odour and bitter taste.
Chemical Constituents:
Tea leaves contain caffeine (1 to 3 percent), theobromine and theophylline (in trace
amount), gallotannic acid (15 percent) and an enzyme mixture known as thease. The colour
of tea leaves is due to the presence of gallotannic acid.
Caffeine is a white powder which is odourless and bitter in taste. It is weakly basic in
nature. It has feeble solubility in water, alcohol, chloroform and ether.
Caffeine is an example of purine group of alkaloids which gives positive Murexide test.
Chemical Test:
1. Murexide test: Take caffeine in a petridish and add hydrochloric acid with potassium chlorate. Heat it upto dryness. Then this obtained residue is exposed to ammonia vapours, a purple colour develops which disappears upon the addition of
alkali solution.
2. When caffeine is treated with tannic acid solution it produces white precipitate.
Uses:
Tea is used as central nervous system stimulant and as diuretic. Caffeine possess cerebral
vasoconstrictor action hence it uses as CNS stimulant. Caffeine also uses in migraine