Norclerodane diterpenoids from rhizomes of Dioscorea bulbifera

Three norclerodane diterpenoids, diosbulbins K-M, and one analogous enolglycoside, diosbulbinoside G, together with four norclerodane diterpenoids, diosbulbins B, E, F and G, were isolated from rhizomes of Dioscorea bulbifera. Their structures were established by spectroscopic and chemical methods, including (1)H and (13)C NMR, NOESY, HSQC, HMBC, and HRMS analyses. The relative configurations of diosbulbins K and L, and diosbulbin F were confirmed by X-ray crystallographic diffraction analysis, and the absolute stereochemistry of diosbulbin K was determined by a modified Mosher's method. The (13)C NMR spectroscopic data for diosbulbins E, F and G were also measured for the first time. The compounds did not show significant cytotoxic and anti-bacterial activities. (C) 2010 Elsevier Ltd. All rights reserved.