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 tea, and they influence aroma and flavor alongside thearubigins. Chemically, they act as antioxidants with redox properties and have been studied for potential health effects, including free radical scavenging and impacts on lipid metabolism in vitro and in some animal studies. However, evidence from human studies remains inconsistent and not conclusive. Theaflavin content is used as a marker of oxidation and processing quality in tea manufacture and can vary with tea cultivar, growing conditions, degree of fermentation, and processing methods.