Separation of glycyrrhizic acid and liquiritin from Glycyrrhiza uralensis Fisch extract by three-liquid-phase extraction systems

Some stable three-liquid-phase extraction systems have been used for isolation and separation of glycyrrhizic acid (GA) and liquiritin (LQ) in aqueous Glycyrrhizia uralensis Fisch extract. Partition behaviors of two compounds were investigated at various conditions. Organic extractants and the pH of solution were two main factors to affect their partitioning among the phases and separation strategies. Different extraction profiles showed that the stronger the electron-donating capability of extractants, the higher the upper-limit of pH in the region for co-extracting GA and LQ, and the higher the lower-limit of pH in the region for stripping GA or LQ from the organic phase. Of all the investigated systems, the three-liquid-phase system containing poly(ethylene glycol-ran-propylene glycol) (EOPO2500) and tri-butyl phosphate (TBP) was the most suitable for separation and purification of licorice extract. FTIR and fluorescence spectroscopic investigations showed that hydrogen bond interaction and hydrophobic interaction among the phases were the main driving forces to affect the partition behaviors of two compounds.