Abstract:In order to realize the efficient extraction,development and utilization of kelp polysaccharides,ultrasonic-assisted deep eutectic solvent （DES） was used to extract kelp polysaccharides,and their antioxidant activity was evaluated.Using kelp as raw material and the amount of polysaccharides extracted from kelp as the evaluation index,it was found that DES composed of choline chloride and lactic acid could be used as the best solvent system.On the basis of sonication for 2.0 h,the process of ultrasonic-assisted DES extraction of kelp polysaccharides was further optimized by single factor experiments,and the Box-Behnken experimental design was further used.A three-way regression model was established to determine the optimal extraction conditions：the optimal extraction temperature was 93 ℃,the optimal molar ratio of choline chloride to lactic acid in DES was 1∶2,and the optimal water content was 20%.Under these conditions,the extraction amount of kelp polysaccharides reached 58.34 mg/g,which was 4.71 times that of the traditional water extraction method.In addition,kelp polysaccharides prepared by this process showed high free radical scavenging rate and iron ion reduction ability.The IC50 for DPPH radical and ABTS+ radical scavenging were 1.53 mg/mL and 0.91 mg/mL,respectively,and the iron ion reduction capacity was 1.12 and the hydroxyl radical scavenging rate was 96.01% when the concentration of kelp polysaccharides was 3.5 mg/mL,indicating ultrasound-assisted DES had the potential to extrac kelp polysaccharides.