Quaternary solvent system for highly efficient separation and purification of glabridin by fractional extraction

• A quaternary solvent extraction system was explored to separate and purify glabridin. • The extraction system is green and simple without reactive extractant. • A mathematical model was established to simulate and optimize extraction process. • Residual rate is introduced to describe product purity and impurity content. • Glabridin with high purity and yield has been obtained continuously. A quaternary solvent extraction system was used to separate and purify glabridin from a crude extract of Glycyrrhiza glabra L. The influence of solvents and their ratios on the distribution of glabridin was examined to develop an efficient quaternary solvent extraction system. For the optimal solvent extraction system, the organic phase consisted of 22.64% butyl acetate, 73.80% hexane, 0.24% water and 3.30% ethanol (W/W), and the water phase consisted of 1.79% butyl acetate, 0.57% hexane, 56.09% water and 41.55% ethanol (W/W). To determine the ideal parameters for separation, a mathematical model was used to simulate and optimize the multi-stage processes. The yield and residual rate were used as the purity reference to simulate the separation of glabridin. Under the optimal conditions, two series of ten-stage and twenty-stage centrifugal extractors were successfully used to separate glabridin. The yield and purity of glabridin were 85% and 94%, respectively, after twenty-stage separation.