14,15-Secopregnane-type C21-steriosides from the roots of Cynanchum stauntonii.

Nine 14,15-secopregnane-type C21-steriosides, stauntosides U, V, V1-V3, W and C1-C3, as well as two known C21-steriosides, were isolated from the roots of Cynanchum stauntonii. Stauntosides U, V and V1-V3 share the same basic structural features of 8α:14α,14:16,15:20,18:20-tetraepoxy-14,15-secopregn-6-ene-3β,5α,9α-triol, with the numbering system following that of C21-pregnanes. The aglycones of stauntosides U, V and V1-V3 are classified into two subcategories, the 5,9-dihydroxy groups and 5α:9α-peroxy bridge, according to the oxidative states of the two hydroxy groups at the C-5 and C-9 positions. The anti-inflammatory activity of the major compounds was assessed in an in vitro inflammatory model of mouse peritoneal macrophages using IC50 values of the inhibition of nitric oxide (NO) production as an indicator. Stauntosides V1 and V3 exhibited target activity with IC50 values of 9.3 μM and 12.4 μM, respectively, compared with dexamethasone, which was used as a positive control.