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

Abstract

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-diginopyranosyl-(1→4)-β-d-cymaropyranosyl-(1→4)-β-d-digitoxopyranosyl-(1→4)-β-d-3′-demethyl-thevetopyranoside. 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. We found that they exhibited significant protective effects on hypoxia/reoxygenation induced cardiomyocyte injury, but did not showed obvious anti-inflammatory function.