Two new casbane diterpenoids from the roots of Euphorbia pekinensis

From the roots of Euphorbia pekinensis, two new casbane diterpenoids, named pekinenins A (1) and B (2), were isolated. Their structures were elucidated as 18-hydroxy-1 beta H,2 alpha H-casba-3E,7E,11E-trien-5-one (1), 5 alpha-methoxy-1 beta H,2 alpha H-casba-3Z,7E,11E-trien-18-oic acid (2) by a combination of 1D and 2D NMR spectroscopy and mass spectrometry. In the cytotoxicity assay of the two new compounds against Hela, MCF-7, and C6 human cancer cell lines, compound 1 showed moderate cytotoxic activity against two human cancer cell lines, Hela and C6, with IC50 values of 42.97 and 50.00 mu M, respectively.