Biological Activities and Functions of Camellia sinensis (Tea)

Tea is an infusion of leaves (or stems/twigs) of the Camellia sinensis plant. It is a very popular drink in the world with a history of more than four thousand years. Tea contains abundant polyphenols (catechins), tannins, flavonols, and methylxanthines (caffeine, theophylline, theobromine). Polyphenolic fl avonoids in tea are potent antioxidants with various biological activities and functions and the chemopreventive effect of green tea is attributed to these polyphenolic compounds, which have been shown to inhibit tumor proliferation. A large number of studies have demonstrated its benefi cial effect on human health. This review attempts to address a general introduction of both bioactive ingredients and various biological activities of tea extracts. In addition, potential drawbacks of tea consumption regarding adverse effects and drug interactions are also mentioned. In summary, daily tea consumption is a recommended behavior to prevent a variety of health disorders though some safety issues should be noted.