Two novel C₂₁ steroidal glycosides from Cynanchum auriculatum

Two new C₂₁ steroidal glycosides, metaplexigenin TC1 (1) and cynanchogenin TC2 (2), were isolated from the roots of Cynanchum auriculatum. Their structures were determined to be meta--plexigenin 3-O-α-L-cymaropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-α-L-cymaropyr-anosyl-(1→4)-β-D-digitoxopyranoside (1) and cynanchogenin 3-O-β-D-cymaropyranos-yl-(1→4)-α-L-diginopyranosyl-(1→4)-β-D-oleandropyranosyl-(1→4)-β-D-cymaropyr-anoside (2) by IR, HRESIMS and NMR experiments. The in vitro NO release inhibition assays gave IC₅₀ values of 76.5 and 53.0 μmol/L, respectively.