Temperature-switchable deep eutectic solvent extraction of polysaccharides from wolfberry fruits: Process optimization, structure characterization, and antioxidant activity

Polysaccharides of wolfberry (LBPs) with complex structures are most commonly used in the food and pharmaceutical industries as biologically active phytochemicals. However, the structure and yield of LBPs vary according to the extraction method used, and selecting their extraction media remains difficult. A novel type of temperature-switchable deep eutectic solvent (TS-DES), consisting of L-menthol and phenyl salicylate, was designed to extract LBPs from wolfberry fruits. TS-DES was a recyclable extractant above the maximum critical solution temperature (UCST). The increased dispersibility of extraction solvents was imparted by combining them with a high-speed shear dispersion emulsification (HSDE) machine. TS-DES was in full contact with the cell walls of wolfberries, leading to the complete opening of the cell walls, resulting in the efficient extraction of LBPs. Compared with traditional extraction, the yield of LBPs-D reached 4.35%, which was higher than that of LBPs-W (1.78%). This study showed that LBPs-D were high molecular weight, highly branched polysaccharides with antioxidant activity. TS-DES was separated at a lower level than UCST for regeneration and reuse. After 5 cycles, TS-DES still had excellent recovery and extraction performance. This study provides valuable information for efficiently extracting structurally rich bioactive polysaccharides from plants using TS-DES.