ANTI-TUMOR-PROMOTING ACTIVITY OF MAJONOSIDE-R2 FROM VIETNAMESE GINSENG, PANAX-VIETNAMENSIS HA ET GRUSHV - (I)

Seven saponins (1-7) isolated from the rhizomes and roots of Panax vie tnamensis were tested for their inhibitory effects on Epstein-Barr vir us early antigen (EBV-EA) induced by the tumor promoter, 12-O-tetradec anoylphorbol-13-acetate (TPA), in Raji cells as a primary screening te st for anti-tumor-promoters (cancer chemopreventive agents). The ocoti llol-type saponin, majonoside-R2 (2), which is the major and character istic constituent of this plant, exhibited a significant inhibitory ef fect on EBV-EA activation. Furthermore, the cell cycle analysis of 2 o n Raji cells was also examined and strong inhibition was observed on t he effect of the cell cycle induced by TPA. Compound 2 showed potent a nti-tumor-promoting activity in two-stage carcinogenesis tests of mous e skin using 7,12-dimethylbenz[a] anthracene (DMBA) as an initiator an d TPA or fumonisin B1 as a promoter, Consequently, these results sugge st that majonoside-R2 (2) could be a valuable chemopreventive agent ag ainst chemical carcinogenesis.