Co-occurrence and high-performance liquid chromatographic separation of the glycosides of rhodeasapogenin and its analogs which differ in the f-ring structure

Two spirostanol glycosides (steroid saponins) R-3 (I) and R-8 (II), which were regarded, respectively, as pure 1-0-α-L-rhamnopyranosyl-(1-2)-β-D-xylopyranoside and 3-0-β-D-glucopyranoside of rhodeasapogenin(25S) (III), were shown by ¹³C-NMR to be accompanied by the corresponding glycosides of isorhodeasapogenin(25R) (IV) and conva-llamarogenin(Δ²⁵⁽²⁷⁾) (V). Qualitative and preparative separation by HPLC of the components of I and II were studied and successfully achieved by a combination of two methods. They consisted equally of not three but four compounds, which were isolated in the pure state. Three of them were identified as the glycosides of III (major), IV and V, while the fourth was considered to have the same sugar moiety as I or II combined with a new aglycone different from III - V in the F-ring structure. The methods were applied also to some commonly known sterod saponins.