Pregnane C21-Steroids with Anti-Inflammatory Activity from the Roots of Cynanchum bungei

Five pregnane C-21-steroids, including three 5,6-epoxy steroids (1-3) and two 8,14-seco-steroids (4 and 5), were isolated from the acid hydrolysate of Cynanchum bungei roots. Cynbungenins L-O (1-4) are previously undescribed compounds. Compound 3 with a 5 alpha,6 alpha-epoxy group represents the first example found in the Cynanchum plants. Their structures and absolute configurations were elucidated by a variety of spectroscopic analysis and theoretical ECD calculations. All compounds (1-5) were evaluated for their anti-inflammatory activity by inhibiting the lipopolysaccharide (LPS)-induced nitric oxide (NO) released in RAW264.7 cells. The results showed that they all possessed NO inhibitory activity at 50 mu M, and compounds 3 and 4 exhibited stronger NO inhibitory activity than indomethacin.