Separation of Mori fructus Polysaccharides and Screening of Bioactive Fractions Based on Membrane Technology

Membrane technology was used for the graded separation of Mori fructus polysaccharides, and its antioxidant, hypoglycemic, anti-allergic and in vitro alcohol dehydrogenase activities were studied. The Mori fructus polysaccharides were carried out by hot water extraction using ultrafiltration membranes with pore sizes of 300, 50, 5 and 1 kDa, respectively, as MFP300, MFP50, MFP5 and MFP1. The differences in the main components, antioxidant activity, hypoglycemic activity, antiallergic activity and in vitro ethanol dehydrogenase activity of Mori fructus polysaccharide fractions separated by ultrafiltration membranes of four pore sizes were compared. The results showed that the major components and biological activities of the four polysaccharides showed some differences. The total sugar content of MFP1, MFP5, MFP50 and MFP300 were 46.34%, 68.45%, 48.60% and 66.32%, respectively, while the glyoxylate content were 3.34%, 22.78%, 16.11% and 21.48%, respectively, and the reducing sugar content were 16.51%, 6.03%, 7.90% and 6.67%, respectively. Bioactivity screening showed that MFP300 scavenged DPPH radicals and ABTS⁺ radicals with IC₅₀ values of 0.2235 and 0.2979 mg·mL⁻¹, respectively, inhibited hyaluronidase with IC₅₀ values of 0.6634 mg·mL⁻¹, and activated in vitro ethanol dehydrogenase with IC₅₀ values of 10.2646 mg·mL⁻¹. MFP300 was exhibited the best antioxidant, anti-allergic and in vitro ethanol dehydrogenase activities compared with the other three components. Compared with the other three components, MFP1 exhibited the best hypoglycemic activity with IC₅₀ values of 0.7944 and 4.6419 mg·mL⁻¹ for its ability to inhibit α-glucosidase and α-amylase, respectively. In conclusion, there were some differences in the main components and biological activities of Mori fructus polysaccharides obtained by membrane classification and separation, which could provide a theoretical basis for the improvement and upgrading of Mori fructus polysaccharide classification technology and the study of the ''structure-effect'' relationship of Mori fructus polysaccharides.