Recently, we and others showed that the components of
green tea may be useful
cancer chemopreventive agents. It has been suggested that (-)-epigallocatechin-3-gallate (EGCG), the major constituent in
green tea, may possess antitumor-promoting and/or
anticarcinogenic effects in rodent
tumor bioassay systems. During the chemical analysis of various
green tea products, we found a traditionally preserved preparation of
green tea used by tribes in the Himalayan region of Sikkim, India that was rich in EGCG. EGCG was isolated from this
tea product, and its inhibitory effects were evaluated against the binding of topically applied 3H-labeled
polycyclic aromatic hydrocarbons (PAHs) to epidermal
DNA and 12-O-tetradecanoylphorbol-13-acetate (TPA) caused induction of epidermal
ornithine decarboxylase (ODC) activity in Sencar mice, the short-term markers of
tumor initiation and
tumor promotion, respectively. Preapplication of EGCG resulted in significant inhibition (p less than 0.05) in the binding of [3H]PAH to epidermal
DNA. Similarly, the topical application of EGCG resulted in significant inhibition (p less than 0.005) in TPA-caused induction of epidermal ODC activity. In further studies, we assessed the anti-skin
tumor-initiating effect of EGCG in Sencar mice in an initiation-promotion protocol. The application of EGCG before challenge with 7,12-dimethylbenz[a]
anthracene as
tumor initiator resulted in significant reduction both in percentage of mice with
tumors and number of
tumors per mouse compared with a non-EGCG-pretreated group of animals. The results of the present study suggest that the
green tea preparation from Sikkim may be a good source for the isolation of EGCG and that this compound may have significant potential as a
cancer chemopreventive agent.