Anti-inflammatory 12,20-Epoxypregnane and 11,12-seco-Pregnane Glycosides from the Stems of Hoya kerrii

Five 12,20-epoxypregnane glycosides (13, 5, and 6) and two 11,12-seco-pregnane glycosides (4 and 7) with spirodilactone motifs, as well as spirodilactone cleavage products 8 and 9, were isolated from the stems of Hoya kerrii. The relative configurations of the three related skeletons were supported by ROESY experiments and X-ray crystallographic analyses. The isolates were evaluated for their anti-inflammatory activity based on the inhibition of NO production in RAW264.7 cells, and some showed IC50 values ranging from 12.6 to 96.5 μM. The most potent compound, 9a, was also examined for its anti-inflammatory mechanism against mRNA expression and was found to down-regulate mRNA expression of iNOS and COX-2 in a dose-dependent manner.