Family Theaceae

Habitat ► Cultivated in Assam, Darjeeling, Travancore, the Nilgiris, Malabar, Bengal, Dehra Dun and Kumaon.

Canarium strictum Roxb.

Siddha/Tamil ► Thaeyilai.

Action ► Stimulant, diuretic, astringent. In China, used for diarrhoea and dysentery (causes gastrointestinal upsets and nervous irritability when consumed in excess). Green tea: anticancer effects have been observed in Chinese green tea, Camellia thea, extract; the extract of Japanese green tea showed antihepatotoxic effects.

Important constituents of leaf buds and very young leaves are: caffeine, with a much smaller amount of other xanthines (theophylline and theo-bromine); tannins (the main tannin in green tea is (-)-epigallocatechin); flavonoids, quercetin, kaempferol. The stimulant and diuretic are due to caffeine content, the astringency due to the tannins.

Drinking tea lowers thiamine and thiamine diphosphate losses in urine and blood serum respectively but increases niacin losses. Hot water extract of black tea facilitates Ca absorption in the body experimentally. Tea may decrease zinc bioavailability.

The tea, if added to the meal, significantly lower the availability of iron. Milk is as effective as ascorbic acid in countering the depressing effect of tea on iron availability (in vitro).

The green tea catechin inhibited car-cinogenesis in small intestines when given during or after carcinogen treatment to experimental rats. (-)-epi-gallocatechin gallate and theaflavin di-gallate from green tea inhibited the in-fectivity of both influenza A and B virus (in vitro).

Green tea, when added to a lard-cholesterol diet, decreased the cholesterol and triglyceride levels in fowls. Tea polyphenols exhibit hypocholes-terolaemic activity.

Tea polyphenols—(-)-epicatechin gallate, (-)-epigallocatechine galate, theaflavin monogallate A or B, and or theaflavin digallate—are used for treating hyperglycaemia.

Saponins from tea are used as an-tiulcer agents.

Concurrent use of tea and beta-adrenergic agonists may increase the risk of cardiac arrhythmias. Caffeine, a component of tea, may increase insulin resistance. (Sharon M. Herr.)

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