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Penta- O -Galloyl-β-D-Glucose and (-)-Epigallocatechin Gallate

1992; American Chemical Society; Linguagem: Inglês

10.1021/bk-1992-0507.ch025

1947-5918

S. Yoshizawa, Takao Horiuchi, Masami Suganuma, Shinji Nishiwaki, Jun Yatsunami, Sachiko Okabe, T. Okuda, Y Muto, Krystyna Frenkel, Walter Troll, Hirota Fujiki,

Phytoestrogen effects and research

Penta-O-galloyl-β-D-glucose (5GG), obtained by methanolysis of tannic acid and (-)-epigallocatechin gallate (EGCG), the main constituent of Japanese green tea, were polyphenols which strongly inhibited the specific 3H-12-O-tetradecanoylphorbol-13-acetate (TPA) binding to the phorbol ester receptors in a particulate fraction of mouse skin. Based on the evidence, these polyphenols were thought to inhibit tumor promotion of TPA on mouse skin. 5GG and EGCG inhibited tumor promotion of teleocidin, one of the TPA-type tumor promoters on mouse skin initiated with 7,12-dimethylbenz(a)anthracene (DMBA) in two-stage carcinogenesis experiments. Moreover, EGCG inhibited tumor promotion of okadaic acid, which acts differently on cells than the TPA-type tumor promoters. The mechanisms of action of EGCG were studied in relation to the reduction of specific binding of the tumor promoters, 3H-TPA and 3H-okadaic acid to their receptors in cell membrane. A single application of 5 mg EGCG decreased immediately to the minimum level the specific binding of 3H-tumor promoters. The effect was understood to be a sealing of the membrane by EGCG, due to EGCG-protein interaction, resulting in reduction of protein phosphorylation in cells. In addition, EGCG inhibited H2O2 formation by TPA-activated human polymorphonuclear leukocytes. Since EGCG is a non-toxic compound, ingested in green tea in every day life in Japan, we extended the study of EGCG as a cancer preventive agent. This paper also reviews inhibitory effects of EGCG on duodenal carcinogenesis of male C57BL/6 mice and development of spontaneous hepatoma in male C3H/HeN mice. We think EGCG is a practical cancer chemopreventive agent to be implemented in every day life.