Rational development of a selection model for solvent gradients in single-step separation of ginsenosides from Panax ginseng using high-speed counter-current chromatography

A new model of solvent gradients selection was rationally developed for the preparative separation of target compounds. The solvent gradients were selected based on a three-stage screening process where stationary phase retention was ensured by introducing a new parameter termed as the phase ratio. The phase ratio was calculated after mixing the upper phase of a solvent system with the lower phase of a different solvent system (1:1, v/v). The developed model was applied to the one-step separation of eight ginsenosides from Panax ginseng. Three gradients were selected on the basis of new model and eight ginsenosides, Rb-1, Rb-2, Rc, Rd, Re, Rg(1), Rf, and Rh-1, were efficiently separated by high-speed countercurrent chromatography coupled with evaporative light scattering detector. The structures of all compounds were characterized by electrospray-ionization mass spectrometry and nuclear magnetic resonance spectroscopy.