Thesis (M.Sc.)--Chulalongkorn University, 1999

Three new labdane diterpenoid compounds, 2-acetoxy-labda-8(17), 12(E), 14-triene-3-ol (1), 3-acetoxy-labda-8(17), 12(E), 14-triene-2-ol (2), labda-8(17), 12(E), 14-triene-2, 3-diol (3) were isolated from the stem bark of Croton oblongifolius Roxb. The structure of the new compounds were established by spectroscopic data (IR, MS spectra, 1D and 2D NMR techniques including DEPT, COSY, NOESY, HMBC and HMQC) and they were tesed for cytotoxicity against various human tumor cell lines (KATO-3 (gastric), SW 620 (colon), BT474 (breast), HEP-G2 (hepatoma) and CHAGO (lung)). Compound 3 showed moderate activities against KATO-3 (gastric), SW 620 (colon), BT474 (breast), HEP-G2 (hepatoma) and CHAGO (lung) cell line. Compound 1 was active against KATO-3 cell line and SW 620 cell line. Compound 2 was active against KATO-3 (gastric) and BT474 (breast) cell line