Green tea leaf

Epidemiologically, it is well known that the consumption of green tea may help to prevent cancers in humans and also to reduce several free radicals including peroxynitrite.

In a recent study to assess the efficacy of the inhibition of mushroom tyrosinase (monophenol monooxygenase EC 1.14.18.1), ten kinds of traditional Korean teas were screened for their tyrosinase inhibitory activity. Green tea was the strongest inhibitor, and its major active constituents are (-)-epicatechin 3-O-gallate (ECG), (-)-gallocatechin 3-O-gallate (GCG) and (-)- epigallocatechin 3-O-gallate (EGCG). All are catechins with a gallic acid group as an active site.

The kinetic analysis of the inhibition of tyrosinase revealed a competitive nature of GCG with this enzyme for Ltyrosine binding at the active site of tyrosinase.

Phenolic compounds from plant sources, particularly flavonoids, have long been observed to have antioxidant activity with potential benefits for human health. Epigallocatechin gallate (EGCG) is a principle phenolic antioxidant found in a variety of plants, including green and black tea.