In this study, the process conditions, physicochemical properties, structural composition and activity of polysaccharides isolated from leechee peel (LPP) by ultrasound-assisted extraction (UAE) with enzyme and alkali solution extraction (ASE) were compared. The results showed that the total sugar content of LPP extracted by UAE accounted for 75.65 %, which was significantly higher than that extracted by alkali solution. The optimum conditions were as follows: extraction temperature of 68.78 ℃, ultrasonic enzymolysis time of 39.68 min, pectinase dosage of 4.03 %, solid-liquid ratio of 1:30 g/mL, and ultrasonic power of 360 W. The antioxidant activities and structure of leechee peel polysaccharide (LPP) prepared under different conditions were compared. It was found that UAE-LPP was an α-type polysaccharide containing 15.83 % uronic acid. Moreover, LPP extracted by UAE showed strong activity in anti-lipid peroxidation and reducing ability. Ultrasound-assisted enzymatic method is an effective means to improve the content and activity of natural plant polysaccharides, and this method has the advantages of short time-consuming, simple process and easy operation, which can greatly improve the utilization rate of polysaccharides and lay a theoretical and scientific basis for the development and utilization of LPP.
Keywords: Alkali solution extraction method; Analysis; Leechee peel polysaccharide; Response surface optimization; Ultrasonic/enzymatic extraction.
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