Inhibitory effects and toxicity of green tea polyphenols for gastrointestinal carcinogenesis

✍ Scribed by Tetsuro Yamane; Hirohisa Nakatani; Norikazu Kikuoka; Hirohiko Matsumoto; Yasushi Iwata; Yoshitaka Kitao; Kazuhiko Oya; Toshio Takahashi

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 504 KB
• Volume: 77
• Category: Article
• ISSN: 0008-543X
• DOI: 10.1002/(sici)1097-0142(19960415)77:8<1662::aid-cncr36>3.0.co;2-w

✦ Synopsis

BACKGROUND.

Recently, an epideiniologic study showed a lower risk of gastrointestinal carcinogenesis in green tea drinkers. An experiment on two-stage skin carcinogenesis in mice showed that (-)-epigallocatechin gallate (EGCG), one of the main constituents of green tea, inhibited tumor formation.

METHODS.

The inhibitory effects of EGCG and green tea extract (GTE) on N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG)-induced duodenal carcinogenesis in the mouse, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis of the glandular stomach in the rat, and azoxymethane-induced colon carcinogenesis in the rat were examined. The toxicity of GTE was assessed experimentally and GTE was applied clinically in normal volunteers to determine the effective dose and to assess its harmful effects.

RESULTS. EGCG and GTE inhibited chemical carcinogenesis of the gastrointestinal

tract in rodents. Judging from the epidemiologic and experimental findings, it was determined that 1 g per day of GTE might be an effective dose. GTE was not toxic and no harmful effect was found during its clinical use.