Cytotoxicity of naturally occurring rhamnofolane diterpenes from Jatropha curcas.

Twelve rhamnofolane diterpenoids, including curcusecons A-E with unusual seco-rhamnofolane skeletons, curcusones F-J, 4-epi-curcusone E, and 3-dehydroxy-2-epi-caniojane, together with seven known analogues, curcusones A-E, jatrogrossidione, and 2-epi-jatrogrossidione, were isolated from the roots of Jatropha curcas. Their structures were determined by extensive spectroscopic methods, and the relative stereochemistry of curcusecon B was further confirmed by X-ray crystallographic data. Their cytotoxity against five human cancer cells was studied and the results indicated that the dienone system in ring B was essential for cytotoxicity of these compounds.