Antitumor activity of norditerpenoid dilactones in Podocarpus plants: structure-activity relationship on in vitro cytotoxicity against Yoshida sarcoma.

The in vitro cytotoxicity of norditerpenoid dilactones isolated from Podocarpus plants was determined against cultured Yoshida sarcoma cells. The dilactones involved 15 natural lactones as well as their derivatives, which include appropriate modifications necessary to the estimation of the structure-activity relationship. The unsaturated system on the B/C ring portion, the dienolide or the epoxyenolide moiety, is essential for the activity, but the gamma-lactone group on the A/B ring portion is not. Other oxygenated substituents on the skeletal carbons, such as hydroxyl, acyloxyl, or epoxide group, also show some significant effect.