Cancer chemopreventive agents (antitumor-promoters) from Ajuga decumbens

Sixteen compounds (1-16) isolated from the flowering whole plant of Ajuga d ecumbens have been tested for their inhibitory effects on Epstein-Barr viru s early antigen (EBV-EA) induction by the tumor promoter, 12-O-tetradecanoy lphorbol-13-acetate (TPA), as a primary screening test for antitumor-promot ers (potential cancer chemopreventive agents). Five compounds (6, 9, and 12 -14) showed strong inhibitory effects on EBV-EA induction. Of these active compounds, two major constituents of this plant, cyasterone (6) and 8-acety lharpagide (13), showed potent antitumor-promoting activities on a mouse-sk in in vivo two-stage carcinogenesis procedure, using 7,12-dimethylbenz[a]an thracene as initiator and TPA as promoter. Further, compound 13 also exhibi ted potent chemopreventive activity in a mouse pulmonary tumor model.