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

Nine 14,15-secopregnane-type C-steriosides, stauntosides U, V, V-V, W and C-C, as well as two known C-steriosides, were isolated from the roots of Cynanchum stauntonii. Stauntosides U, V and V-V 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 C-pregnanes. The aglycones of stauntosides U, V and V-V 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 IC values of the inhibition of nitric oxide (NO) production as an indicator. Stauntosides V and V exhibited target activity with IC values of 9.3 μM and 12.4 μM, respectively, compared with dexamethasone, which was used as a positive control.