Inhibitory effects of triptogelin A-1 on 12-O-tetradecanoylphorbol-13- acetate-induced skin tumor promotion.

Dihydroagarofuran sesquiterpenes, which were isolated from Tripterygium wilfordii Hook fil. var. regelii Makino and Euonymus sieboldianus Blume, showed inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Triptogelin A-1, one of the active dihydroagarofuran sesquiterpenes, exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. Interestingly, triptogelin A-1 was more effective when applied after TPA-treatment (post-treatment) than before TPA-treatment (pretreatment). The findings indicate that these dihydroagarofuran sesquiterpenes might be valuable antitumor promoters.