New norclerodane diterpenoids from bulbils of Dioscorea bulbifera L.

Abstract

Investigation of extracts from bulbils of Dioscorea bulbifera L. yielded two new norclerodane diterpenoids, diosbulbin N acetate (1) and epi-diosbulbin B (3), together with eleven known compounds. Their structures were established based on spectroscopy. The absolute configurations of 1 and diosbulbin B (2) were determined by X-ray crystallographic analysis using Cu K radiation. The absolute configuration of 3 was determined by comparison of its ECD spectrum to that of 2. Isolated phenanthrenes 7, 9 and 10 exhibited moderate cytotoxicity against the HelaS3 cell line with IC50 values of 9.030.04, 27.136.86 and 10.882.75 M, respectively.In addition, 7-9 and 11 showed potent inhibition of NO production by LPS-induced RAW 264.7 macrophages.