Objective To study the chemical structures of saponins in the rhizome of Cynanchum otophyllum (Asclepiadaceae), and to find new compounds. Methods The total saponins of the rhizome were separated by silica gel column chromatography. The chemical structures of obtained compounds were determined by NMR and FAB-MS spectra. Results Three C21 steroidal saponins were separated. Their structures were determined as caudatin 3-O-β-d-glucopyranosyl-(1→4)-β-d-digitoxopyranosyl-(1→4)-β-d-digino- pyranosyl-(1→4)-α-d-oleandropyranoside (1), caudatin 3-O-β-d-oleandropyranosyl- (1→4)-α-d-oleandropyranosyl-(1→4)-α-d-oleandropyranoside (2), and caudatin 3-O- β-d-glucopyranosyl-(1→4)-α-d-oleandropyranosyl-(1→4)-β-d-diginopyranosyl-(1→4)- α-d-oleandropyranoside (3), respectively. Conclusion Saponins 1-3 are new compounds.
