Deep eutectic solvents used as adjuvants for improving the salting-out extraction of ursolic acid from Cynomorium songaricum Rupr. in aqueous two-phase system

Abstract

Deep eutectic solvents (DESs) were considered as a good alternative to conventional ionic liquids (ILs) used in the extraction and separation field. Therefore, the aqueous two-phase system (ATPS) formed by ethanol and salt was used for the salting-out extraction (SOE), preconcentration, and preliminary purification of ursolic acid (UA) from Cynomorium songaricum Rupr. (C. songaricum) using various DESs as adjuvants in this study. The DES choline chloride-oxalic acid (ChCl-OA) was screened as the optimal adjuvant, which can play a dual role of enhancing the extraction yield in the preparation of the crude extract and adjusting the distribution of UA in ATPS. The factors influencing the solid-liquid extraction, including type and amount of DESs, ethanol concentration, and solid-liquid ratio were investigated. Then, the major factors influencing the SOE, including salt type and concentration, extraction temperature, and system pH were also optimized. The maximum extraction yield of 108 mg/g in the solid-liquid extraction and the maximum extraction efficiency of >99% in the SOE were obtained, respectively. The recovery of UA from the solution was done using water as the anti-solvent with almost 96.6% UA being recovered, the purity of recovered UA reached 73.5%. This SOE using DESs as adjuvants has the advantages of high extraction efficiency, simple operation, low cost and good environmental friendliness, which is potential for the scale-up application.