New cleistanthane diterpenoids and 3,4-seco-cleistanthane diterpenoids from Croton oblongifolius
Two new cleistanthane-type diterpenoids, 3-hydroxycleistantha-13(17),15-diene (1) and 3,4-seco-cleistantha4(18),13(17),15-trien-3-oic acid (2), were isolated from the stem bark of Croton oblongifolius Roxb. Epoxidation of 2 gave two epoxides 3 and 4. Their structures were established on the basis of spectroscopic data. Compound 1 showed nonspecific strong cytotoxicity against human tumor cell lines, compound 2 showed weak activity, and compounds 3 and 4 were inactive.
Key wordsCroton oblongifolius cleistanthane diterpenoids cytotoxicity
We thank the Thailand Research Fund (DBG4880013), the Thai Government (Nan), and the Graduate School and Department of Chemistry, Faculty of Science, Chulalongkorn University for financial support.