EGCG

Definition

Epigallocatechin gallate (EGCG) is one of the four main catechins in tea and usually the largest, often accounting for around half of the total catechin content of green tea. Structurally, it is epigallocatechin with a gallic acid group (galloyl ester) attached, which gives it a strong ability to bind proteins and adds to its astringency. EGCG is concentrated in young leaves and buds and increases with sunlight exposure. Unshaded green teas therefore contain more than shaded teas such as gyokuro. During the oxidation that produces oolong and black tea, much of the EGCG is converted, along with the other catechins, into theaflavins and thearubigins, so black tea contains far less of it than green tea. EGCG is the most heavily studied compound in tea and is the subject of extensive laboratory research. Results from laboratory and animal studies do not translate directly into effects from drinking tea, and concentrated green tea extract supplements, which deliver far more EGCG than brewed tea, have been linked to liver injury in some cases. Normal tea drinking delivers much smaller amounts.