Chemical constituents of stem bark of Croton oblongifolius from Amphoe Phanat Nikhom, Chon Buri Province

Three clerodane compounds, (-)-hardwickiic acid (1), (-)-patagonic acid (2) and nasimalun A (3) were isolated from the stem bark of Croton oblongifolius from Amphoe Phanat Nikhom, Chon Buri Province. One derivative of compound 1 was synthesized as (-)-hardwickiic acid methyl ester (1a) and a derivative of compound 2 was synthesized as (-)-patagonic acid methyl ester (2a) and three derivatives of compound 3 were synthesized as methyl-15,16-epoxy-3-methoxy-12-oxo-13(16),14-clerodadien-18,19-olide-17-carboxylate (3a), methyl-12,17-dihydroxy-15,16-epoxy-13(16),14-clerodadien-18,19-olide (3b) and methyl-12,17-dihydroxy-15,16-epoxy-3,13(16),14-clerodatrien-18,19-olide (3c). The structure of these compounds were established by physical properties and spectroscopic data. All of the compounds were tested for cytotoxicity against six human tumor cell lines in vitro including Hep-G2 (hepatoma), Chago (lung), SW 620 (colon), Kato-3 (gastric), BT 474 (breast) andHuCCA-1 (human bile duct epithelial carcinoma). Compound 1 and 1a showed weak activity against three tumor cell lines. Moreover, this is the first report of cytotoxicity test of (-)-hardwickiic acid methyl ester (1a), (-)-patagonic acid (2), (-)-patagonic acid methyl ester (2a), nasimalun A (3) and nasimalun A derivatives (3a, 3b and 3c)