Deep eutectic solvents aqueous two-phase system based ultrasonically assisted extraction of ursolic acid (UA) from Cynomorium songaricum Rupr.

Deep eutectic solvents (DESs) are new green solvents that have attracted the attention of the scientific community mainly due to their unique properties and special characteristics, which are different from those of traditional solvents. A method based on ultrasonically assisted deep eutectic solvent aqueous two-phase systems (UAE-DES-ATPS) was developed for extracting ursolic acid (UA) from Cynomorium songaricum Rupr. Four different types of choline chloride-based DESs were prepared. Choline chloride-glucose (ChCl-Glu) exhibited good selective extraction ability. An optimum DES-ATPS of 36% (w/w) ChCl-Glu and 25% (w/w) K2HPO4 was considered to be a satisfactory system for extracting UA. Response surface methodology (RSM) method was utilized to optimize the extraction of UA using UAE-DES-ATPS. The quadratic models were extremely significant (p < 0.01) for all the parameters studied with high correlation coefficients (R2) of 0.9593. The optimum ultrasound-assisted conditions were as follows: solvent to solid ratio of 15:1 (g/g), ultrasound power density of 4.7 W·mL−1, and extraction time of 54 min. Compared with the conventional UAE method, the yields were basically the same, but the presented method had higher purity. The structure of UA did not change between pure UA and UA in the upper phase using UV–vis and FT-IR. This approach using ChCl-based DES-ATPS as a novel extraction system and ultrasound as a source of energy provided a better choice for the separation of active components from other natural products.