Nature's Lab - Green Tea Extract 50% EGCG 500 mg. - 90 Capsules Nature's Lab Green Tea Extract 50% EGCG supports increased metabolism. Green Tea Extract contains polyphenols including epigallocatechin-3-gallate (EGCG), a powerful antioxidant which has been the subject of extensive scientific research. The antioxidant activity of EGCG is about 25–100 times that of vitamins C and E.