Chemical constituents with cytotoxicity of Croton oblongifolius from Nan province

Two novel diterpenoid compounds, 3-hydroxycleistantha-13(17),15-diene (1) and 3,4-seco-cleistantha-4(18),13(17),15-trien-3-oic acid (2) were isolated from the stem bark of Croton oblongifolius Roxb. from Amphur Veingsa, Nan Province. And two derivatives were modified by epoxidation of compound 2 to obtain 3,4-seco-13,17-epoxycleistantha-4(18), 15-dien-3-oic acid (3) and 3,4-seco-8,15-epoxypimara-4(18),15-dien-3-oic acid (4). The structure of new compounds were established by spectroscopic data (IR, MS, 1D, 2D NMR techniques including DEPT, COSY, NOESY, HMBC and HMQC) and they were tested for cytotoxicity against various human tumor cell lines SW620 (colon), BT474 (breast), KATO-3 (gastric), HEP-G2 (hepatoma) and CHAGO (lung). The result showed that compound 1 was active against SW620 (colon), KATO-3 (gastric), HEP-G2 (hepatoma) and CHAGO (lung) cell line with the IC50 values of 0.5, 6.0, 6.1 and 5.5 g/mL, respectively. Compound 2 showed mild activities against SW620 (colon) and KATO-3 (gastric) cell line with IC[subscript 50] values of 8.6 and 9.6 microgram/mL, respectively. Compound 3 and 4 were inactive against all cell lines