Flavonoids are a class of water-soluble plant pigments and it is the catechin called Epigallocatechin-3-gallate (EGCG) in Green Tea that is particularly beneficial. EGCG contains 3 phenol rings and therefore has very strong antioxidant properties.

EGCG is the main active component in Green Tea leaves. Black Tea leaves also contain EGCG but in much lower quantities. Studies have shown that Green Tea has 5 times the EGCG content of regular tea. This is because Black Tea leaves are fermented, during which many of the catechins are oxidized to darker coloured molecules (theaflavin and thearubigen).

EGCG possess the most potent antioxidant activity of the catechins. ECGC may provide health effects by protecting our cells from oxidative damage from free radicals. A number of chronic diseases have been associated with free radical damage, including cancer, arteriosclerosis, heart diseases and accelerated aging. ECGC interferes with many enzyme systems: it inhibits fast-binding and reversible fatty acid synthesis, increases tyrosine phosphorylation of the insulin receptor, activation of ornithine decarboxylase. ECGC can protect the DNA in the human cells from ultraviolet and visible radiation-induced damage. ECGC may be effective in promoting fat oxidation and lowering body weight.