Identification of new qingyangshengenin and caudatin glycosides from the roots of Cynanchum otophyllum

HPLC analysis of the roots of Cynanchum otophyllum Scheind (Asclepiadaceae) led to the isolation of six new pregnane glycosides, specifically otophyllosides N-P (2-4) and otophyllosides Q-S (7-9), in addition to the identification of three known C-21 steroidal glycosides, otophylloside A (1), otophylloside B (5) and caudatin 3-O-β-D-glucopyranosyl-(1→4)-β-D-oleandropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-β-D-cymaropyranoside (6). The structure of each glycoside was determined by detailed spectroscopic analysis and chemical methods. All compounds contain qingyangshengenin or caudatin aglycones and a straight sugar chain consisting of 4-7 hexosyl moieties with the mode of 1→4 linkage. The optically isomeric monosaccharides, D- and L-cymarose, coexisted in both otophyllosides R (8) and S (9).