Inhibitory effect of topical application of a green tea polyphenol fraction on tumor initiation and promotion in mouse skin.

A green tea polyphenol fraction was evaluated for its ability to inhibit tumor initiation by polycyclic aromatic hydrocarbons and tumor promotion by a phorbol ester in the skin of CD-1 mice. Topical application of the green tea polyphenol fraction inhibited benzo[a]pyrene- and 7,12-dimethylbenz[a]-anthracene-induced tumor initiation as well as 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion. Topical application of the green tea polyphenol fraction also inhibited TPA-induced inflammation, ornithine decarboxylase activity, hyperplasia and hydrogen peroxide formation. Studies with individual polyphenolic compounds in green tea indicated that topical application of (-)-epigallocatechin gallate, (-)-epigallocatechin and (-)-epicatechin gallate inhibited TPA-induced inflammation in mouse epidermis.