In the course of our continuing search for novel cancer chemopreventive agents from natural sources, several kinds of Panax plants were screened. Consequently, the ocotillol-type saponin, majonoside-R2 (MR2), was obtained from the rhizome and root of Panax vietnamensis (Vietnamese ginseng) as an active constituent. MR2 exhibited potent anti-tumor-promoting activity on two-stage carcinogenesis test of mouse hepatic tumor using N-nitrosodiethylamine (DEN) as an initiator and phenobarbital (PB) as a promoter. Further, MR2 exhibited the remarkable inhibitory effect on two-stage carcinogenesis test of mouse skin induced by nitric oxide (NO) donor/12-O-tetradecanoylphorbol-13-acetate (TPA) or peroxynitrite/TPA. Copyright (C) 1999 Elsevier Science Ireland Ltd.
