Polyhydroxypregnane glycosides and deoxyoligosaccharides from Cynanchum acutum subsp. sibiricum and anticomplementary activity of its compounds

Two new polyhydroxypregnane glycosides, named as cynacutosides A and B (1 and 2), and one new deoxyoligosaccharide, named as cyoligose A (3), together with two known analogues (4 and 5), one known polyhydroxypregnane glycoside (6) and a C₂₁ steroid (7), were isolated from the roots and rhizomas of Cynanchum acutum subsp. sibiricum. Three new compounds were identified as sarcostin 3-O-β-D-oleandropyranoside, 12-O-deacetylmetaplexigenin 3-O-β-D-oleandropyranoside, and β-D-oleandropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-1-methyl-β-L-diginopyranoside by spectroscopic methods including 2D-NMR techniques. The known compounds were determined spectroscopically and compared with previously reported spectral data. Compounds (1-7) exhibited anticomplementary effects against the classical pathway (CP) with CH₅₀ values from 0.23 mM to 1.89 mM, which are plausible candidates for developing potent anti-complementary agents from this plant.