Optimization of ultrasound-assisted deep eutectic solvent extraction, characterization, and bioactivities of polysaccharide from the fruit of Rosa roxburghii Tratt

The polysaccharide was extracted by ultrasonic-assisted method with deep eutectic solvent from Rosa roxburghii Tratt. (RRT). The single-factor experiment was carried out first, and then the response surface experiment was designed to obtain the optimal process conditions. The optimal extraction conditions were the molar ratio of choline chloride to oxalate of 1:1, the water content of deep eutectic solvent (DES) of 27%, the solid-liquid ratio of 1:52 g/mL, time of 99 min, and the power of 240 W, with the extraction yield of 3.397%. The yield of RRT polysaccharide (RRTP) was 2.693% and 2.521% by water immersion and ultrasonic water extraction, respectively, indicating that the DES extraction method (3.397%) is superior to these two methods, and the optimization effect is good. After purification by the DEAE-SephaRosa (DEAE) column and Sephadex G-75 column, the biological activities of the extracted polysaccharides were tested. At a concentration of 6.4 mg/mL, RRTPs-1 inhibited α-glucosidase by 26%. The IC 50 value of RRTPs-1 against α-amylase was 2.94 mg/mL. At 3.2 mg/mL, RRTPs-1 inhibited DPPH· by 22.36%. The IC 50 value of RRTPs-1 on ABTS· + scavenging was 0.055 mg/mL. The analysis of monosaccharide composition shows that it contains glucose, rhamnose, xylose, arabinose, mannose, galactose, galacturonic acid, and glucuronic acid, with the molar ratio of 1.00: 14.14: 4.28: 5.63: 15.47: 64.50: 5.03: 41.43. In this paper, the process of extracting RRTP with deep eutectic solvent was studied and optimized. The activity study showed that RRTP has certain hypoglycemic and antioxidant activities. Therefore, this study can provide an experimental basis for the establishment of an industrialized production process of polysaccharides and the study of their biological activities.