Preparative isolation and purification of five steroid saponins from Dioscorea zingiberensis C.H.Wright by counter-current chromatography coupled with evaporative light scattering detector

A counter-current chromatography (CCC) method was successfully applied to separate and purify steroid saponins from the traditional Chinese medicine Dioscorea zingiberensis C.H.Wright for the first time. Ethyl acetate-n-butanol-methanol-water (4:1:2:4, v/v) was used as the two-phase solvent system, and evaporative light scattering detector (ELSD) was used as the detector in this method. The method separated in a single run the following five steroid saponins: 26-O-β-d-glucopyranosyl-(25R)-furost-5-en-3β, 22ζ, 26-triol-3-O-[β-d-glucopyranosyl-(1→3)-β-d-glucopyranol-(1→4)-α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranoside (Compound A); 26-O-β-d-glucopyranosyl-(25R)-furost-5-en-3β, 22ζ, 26-triol-3-O-[β-d-glucopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)]-β-d-glucopyranoside (Compound B); 26-O-β-d-glucopyranosyl-(25R)-furost-5-en-3β, 22ζ, 26-triol-3-O-[α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranoside (Compound C); 26-O-β-d-glucopyranosyl-(25R)-furost-5, 20(22)-diene-3β, 26-diol-3-O-{α-l-rhamnopyranosyl-(1→4)-[β-d-glucopyranosyl-(1→3)-β-d-glucopyranosyl-(1→2)]}-β-d-glucopyranoside (Compound D); and 26-O-β-d-glucopyranosyl-(25R)-furost-5, 20(22)-diene-3β, 26-diol-3-O-[β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranosyl(1→2)]-β-d-glucopyranoside (Compound E). Their structural identification of the five steroid saponins was performed by means of ESI-MS, and (13)C NMR.