Hybrids of 3alpha-methoxyserrat-14-en-21beta-ol (PJ-1) and 3beta-methoxyserrat-14-en-21beta-ol (PJ-2) and various anti-oxidants as cancer chemopreventive agents.

3alpha-methoxyserrat-14-en-21beta-ol (1) and 3beta-methoxyserrat-14-en-21beta-ol (2) and their conjugates with curcumin, kojic acid, quercetin, and baicalein (3-18), as well as new analogs (19-24) derived from 1 and 2, were tested for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). The inhibitory effects of 16 (IC50=330 mol ratio/32 pmol/TPA), 9 (IC50=335), 10 (IC50=338), and 15 (IC50=350) were stronger than those of the other compounds and the positive control, oleanolic acid (IC50=449). Compounds 15 and 16, which are conjugates of one molecule each of 1 or 2 and quercetin, inhibited mouse skin tumor promotion in an in vivo two-stage carcinogenesis model. The in vivo two-stage mouse skin carcinogenesis test employed 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.