Large-scale separation of alkaloids from Gelsemium elegans by pH-zone-refining counter-current chromatography with a new solvent system screening method.

A rapid and simple solvent system screening method was developed for pH-zone-refining counter-current chromatography (CCC) separation, which was much easier to find a suitable solvent system than the traditional method. Using this method, an optimal solvent system composed of hexane-ethyl acetate-methanol-water (3:7:1:9, v/v) was selected for pH-zone-refining CCC separation of alkaloids from the stems of Gelsemium elegans, where 10mM triethylamine (TEA) was added to the upper organic stationary phase as a retainer and 10mM hydrochloric acid (HCl) to the aqueous mobile phase as an eluter. As a result, six oxindole alkaloids, 420mg 19-xo-gelsenicine, 456mg gelsemine, 723mg koumine, 379mg 11-methoxygelsemamide, 342mg gelsenicine and 318mg humantenine were successfully purified in one step from 4.5g crude extract with the purity of over 95%, respectively. The structures of the oxindole alkaloids were identified by ESI-MS, (1)H NMR and (13)C NMR.