Steroidal glycosides from Cynanchum forrestii Schlechter

Nine new steroidal glycosides, cynaforrosides B (2), C (3), D (4), E (5), and F (6), based on a 13, 14: 14, 15-disecopregnane-type skeleton, cynaforrosides G (7), H (8), and I (9) with a new aglycone named cynaforrogenin A, and cynaforroside J (10) together with three known C21 steroidal glycosides cynatratoside A (1), hancoside (11) and komaroside C (12) were isolated from the ethanol extract of the roots of Cynanchum forrestii Schlechter. The structures of new compounds were determined on the basis of spectral and chemical evidence. Steroidal glycosides with three kinds of skeletons were isolated from this plant simultaneously. The sugar units of cynaforrosides B-I contained two moieties of glucoses and especially cynaforrosides E-I contained two glucoses with the mode of 1 → 6 linkage, which were rare among steroidal glycosides of the genus Cynanchum.