Pregnane C21‐Steroids with Anti‐inflammatory Activity from the Roots of Cynanchum bungei

Five pregnane C21‐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 5a,6a‐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 μM, and compounds 3 and 4 exhibited stronger NO inhibitory activity than indomethacin.