Tea is one of the most popular beverages consumed worldwide. Freshly harvested tea leaves are converted into green, oolong and black teas during processing. More than 75% of the world tea products are black tea, and polyphenols in black tea contribute to the majority of its reported biofunctions. In this paper we review the chemistry properties of polyphenols and bio-function properties including taste, anti-inflammation and anti-cancer. In the course of studies on the oxidation mechanisms of tea polyphenols, a new type of a tea pigment, theadibenzotropolone A, together with theaflavin 3-gallate were formed in the reaction of (-)-epicatechin (EC) and (-)-epigallocatechin gallate (EGCG). Theaflavins and flavon-3-ol glycosides have been shown to give an astringent perception with low threshold. Theaflavins have also demonstrated strong capabilities of anti-inflammation and anti-cancer via the NF-AB and MAPKs pathways, respectively.
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