Sugar-free pregnane-type steroids from the roots of Cynanchum stauntonii.

Two new sugar-free 14,15-secopregnane-type steroids, 14-O-methyl-3-epi-hirundigenin (1) and 2-deoxyamplexicogenin A (2), along with two known sugar-free pregnane-type steroids, were isolated from the 95% ethanol extract of the roots of Cynanchum stauntonii. The structures of the new compounds were characterized on the basis of extensive spectroscopic analyses, mainly 1D and 2D NMR methods, albeit the MS experiments did not display the molecular ion peaks. Compound 2 was the aglycones of stauntosides J and K, etc., previously isolated from C. stauntonii. The isolation and identification of the new compounds graced the structural diversity of pregnane-type steroids from C. stauntonii.