Optimization of Repeated Freezing-Thawing Reflux for Extraction of Polysaccharide from Hovenia dulcis and Its Antioxidant Activity

In order to extract more polysaccharide from Hovenia dulcis and improve the antioxidant activity of the extract, repeated freezing-thawing technology coupled with reflux extraction method was employed, and major freezing-thawing conditions affecting the content of polysaccharide were optimized via orthogonal tests; In the end, the antioxidant activity of polysaccharide extract was evaluated. The results indicated that the optimal freezing-thawing conditions were as follows: The water content for swelling was set at 40 mL/100 g, freezing time was 4 h, the time of repetition of freezing-thawing was twice, and thawing temperature was 60 °C, under which the content of polysaccharides in Hovenia dulcis studied was 1.68%±0.03%. The clearance rates of polysaccharide extract to DPPH free radical and ABTS free radical were up to 86.73% (when the concentration of extract was 0.10 mg/mL) and 91.33% (when the concentration of extract was 2.0 mg/mL), respectively. The results provide a reference for the comprehensive utilization of polysaccharide from Hovenia dulcis.