Pregnane glycosides from Cynanchum atratum

Five new pregnane glycosides, cynanosides K–O (1–5) with a 14,15-seco-pregnane-type skeleton as the aglycon, together with five known compounds, cynascyroside C, sublanceoside E1, sublanceoside I1, atratoside A and atratoside B, were isolated from the roots of Cynanchum atratum. Their structures were determined on the basis of spectroscopic analysis and chemical evidence.