Three new diterpenes from Jatropha curcas

Jatrophalactone (1) and jatrophalone (2), together with jatrophadiketone (3), a 6/6/6 tricyclic diterpene transformed from rhamnofolane skeleton, have been isolated from the methanolic extract of Jatropha curcas. The structures were established on the basis of extensive spectroscopic methods and further confirmed by X-ray crystallographic analysis. The cytotoxicity against selected cell lines was evaluated. Among them, compound 1 displayed cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cell lines with IC50 values of 8.5, 20.6, 19.7, 20.1, and 19.2 μM, respectively. The possible biosynthetic pathways for 1 and 3 are proposed.