Twelve pregnane glycosides from Cynanchum atratum

Eleven new 14,15-seco-pregnane-type steroidal glycosides, cynanosides P1–P5, Q1–Q3, R1–R3, and a novel 12,13-seco-14,18-nor-pregnane-type steroidal glycoside, cynanoside S, were isolated from the roots of Cynanchum atratum, together with four known compounds, atratoside C, sublanceoside E3, chekiangensoside C and cynatroside B. Their structures were determined on the basis of spectroscopic analysis and chemical evidence.