Abstract:In this study, Polygonatum sibiricum polysaccharides (PSPs) were extracted by deep eutectic solvents(DESs) with different ion combinations. The optimal effect of urea-choline chloride deep eutectic solvents was obtained. Based on single factor investigation, response surface analysis was used to investigate the optimum conditions for the extraction of PSPs by urea-choline chloride eutectic solvent. And the effect of DESs reuse on the extraction rate and content of PSPs was studied. The antioxidant activity of the PSPs in vitro was determined by measuring the total antioxidant capacity, O-2 free radicals and DPPH free radical scavenging rate. The results showed that the optimum process parameters for PSPs extraction by DESs were as follows:temperature 70℃, urea-choline chloride molar ratio 1.19, extraction time 42.30min, liquid to material ratio 20.75mL/g. Under this condition, the extraction rate of PSPs was 18.55%, and the relative error was 2.69% compared with the predicted value, which was 139.97% higher than that extracted by the traditional hot water. The DESs reuse not only had no effect on the extraction rate of PSPs, and the maximum was 83.9% higher than that of fresh solvents when reusing for the third time; and the content of PSPs increased continuously and tended to be stable with increasing the repeated times. After 4 or 5 times of reuse, the PSPs content was basically stabilized at 63.48% and 64.12%, respectively, which indicated that the purity was increasing. The total antioxidant capacity, scavenging rate of O-2 free radical and DPPH free radical was in dose dependent manner with mass concentration of PSPs, which was increased with the increase of mass concentration. The total internal antioxidant capacity was 241.2μg/mL, and the IC50 of O-2 free radicals and DPPH free radical scavenging capacity were 0.524mg/mL and 0.951mg/mL, respectively. Therefore, the DESs method was a new high-efficiency, clean and environment friendly method for extracting the Polygonatum sibiricum polysaccharides.