New 19-acetoxyingol diterpenes from the latex of Euphorbia poisonii (Euphorbiaceae).

The poisonous latex of Euphorbia poisonii gave bioactive 3,12-diacetyl-8-nicotinyl-7-phenylacetyl 19-acetoxyingol (1) together with its less active congeners, 3,12-diacetyl-7-phenylacetyl 19-acetoxyingol (2) and 3-acetyl-7-phenylacetyl 19-acetoxyingol (3). The chemical structures of 1-3 were determined by spectroscopic methods including HRMS, DEPT, HETCOR, COSY, NOESY, HMQC and HMBC. The absolute configurations of the hydroxylated carbons in 2 and 3 were provisionally suggested by the Mosher ester method. Bioactivity-guided isolation, structure determination and cytotoxic activity of the new ingols are described.