New C21 steroidal glycosides from the roots of Cynanchum stauntonii and their protective effects on hypoxia/reoxygenation induced cardiomyocyte injury

Phytochemical investigations from the roots of Cynanchum stauntonii led to obtain four new C₂₁ steroidal glycosides (1-4) and one known compound stauntoside F (5). Their chemical structures were characterized by sophisticated analyses of IR, HRESI-TOF-MS, 1D, and 2D-NMR data, together with chemical methods, which showed interesting 13,14:14,15-disecopregnane-type skeleton or 14,15- secopregnane-type skeleton C₂₁ steroidal glycosides. Among them, compound 1 was determined to be glaucogenin C 3-O-β-D-glucopyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-β-D-digitoxopyranosyl- (1→4)-β-D-thevetopyranoside. Compound 2 was characterized to be hirundigenin 3-O-α-L-diginopyr-anosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-β-D-digitoxopyranosyl-(1→4)-β-D-3'-demethyl-theveto-pyranoside. Compound 3 was identified to be (14S,16S,20R)-14,16-14,20-15,20-triepoxy-14,15-secopregn- 5-en-3-ol-3-O-α-L-cymaropyranosyl-(1→4)-β-D-digitoxopyranosyl-(1→4)-β-D-oleandropyranoside. Compound 4 was identified to be (14S,16S,20R)-14,16-14,20-15,20-triepoxy-14,15-secopregn-5-en-3-ol- 3-O-α-L-cymaropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-β-D-digitoxopyranosyl-(1→4)-β-D-thevetopyranoside. Among them, compound 2 was hirundigenin type C₂₁ steroidal glycoside that existed in nature as epimers due to the presence of 14-hemiketal hydroxyl group in its structure. In addition, the anti-inflammatory and cardiomyocyte protective effects of compounds 1-4 were evaluated.Wefound that they exhibited significant protective effects on hypoxia/reoxygenation induced cardiomyocyte injury, but did not showed obvious anti-inflammatory function.