Green tea polyphenols and cancer chemoprevention: multiple mechanisms and endpoints for phase II trials.

Among the numerous polyphenols isolated from green tea, the catechin EGCG predominates and is the target of anticancer research. But studies suggest that EGCG and other catechins are poorly absorbed and undergo substantial biotransformation to species that include glucuronides, sulfates, and methylated compounds. Numerous studies relate the antioxidant properties of the catechins with anticancer effects, but recent research proposes other mechanisms of action, including those involving methyl transfers that are subject to allelic variability in the enzyme catechol O-methyl transferase. However, preclinical research is promising and EGCG appears to be ready for further study in phase II and III trials.