theaflavins
Theaflavins are a class of polyphenolic compounds found predominantly in black tea. They are oxidized dimers of flavan-3-ols formed during the enzymatic oxidation of catechins in tea leaves as they are processed (fermented) to black tea. The key reactions occur during withering, rolling, and fermentation; polyphenol oxidase catalyzes the coupling of catechin and/or gallocatechin units to give theaflavins and related pigments such as thearubigins. The major theaflavins are theaflavin (TF1), theaflavin-3-gallate (TF2a), theaflavin-3'-gallate (TF2b), and theaflavin-3,3'-digallate (TF3).
Theaflavins contribute to part of the orange-red color and to the brisk astringency characteristic of black