Anti-carcinogenic activity of Taraxacum plant. II

Eleven triterpenoids (1-11) from the roots of Taraxacum japonicum (Composit ae) were examined for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) induced by the tumor promoter 12-O-tetradecanoylphorbol-13 -acetate (TPA), in Raji cells as a primary screening test for anti-tumor-pr omoters (cancer chemopreventive agents). Of these triterpenoids, taraxaster ol (1) and taraxerol (7) exhibited significant inhibitory effects on EBV-EA induction, but the inhibitory effects of their acetates 2 and 8 were weake r than those of 1 and 7, Furthermore, 1 and 7 exhibited potent anti tumor-p romoting activity in the two-stage carcinogenesis tests of mouse skin using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promote r, and 1 showed a remarkable inhibitory effect on mouse spontaneous mammary tumors using,C3H/OuJ mouse, These results strongly suggested that taraxast erol (1) could be a valuable chemopreventive agent.