Anti-tumor promoting activity of polyphenols from Cowania mexicana and Coleogyne ramosissima

Chemical investigation on polyphenol-rich fractions of Cowania mexicana and Coleogyne ramosissima (Rosaceae) which showed significant inhibitory effec ts on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O- tetradecanoylphorbol-13 -acetate (TPA), has led to the characterization of 10 compounds including C-glucosidic ellagitannin monomers and dimers from t he former plant, and 17 polyphenols including flavonoid glycosides from the latter. The effects of individual components and their analogues with rela ted structures on the TPA-induced EBV-EA activation were then evaluated. Am ong the compounds isolated from C. mexicana, two C-glucosidic ellagitannins , alienanin B and stenophyllanin A and a nitrile glucoside (lithospermoside ), and among the constituents from C. ramosissima, two flavonoid glycosides , isorhamnetin 3-O-beta-D-glucoside and narcissin were revealed to possess strong inhibitory effects on EVB-EA activation, the potencies of which were either comparable to or stronger than that of a green tea polyphenol, (-)- epigallocatechin gallate. These polyphenols except for nitrile glucoside, w hich was not tested owing to an insufficient amount, were also found to exh ibit anti-tumor promoting activity in two-stage mouse skin carcinogenesis u sing 7,12-dimethylbenz[a]anthracene (DMBA) and TPA. (C) 1999 Elsevier Scien ce Ireland Ltd. All rights reserved.