Study on the Preparation and Antioxidant Activity of Low Molecular Weight Polysaccharide from Cudrania tricuspidata Fruits

Objective: The molecular weight Cudrania tricuspidata Fruits polysaccharide was prepared and the effect of different molecular weight on their antioxidant activity was further explored. Methods: The low molecular weight cudge polysaccharide was prepared by H₂O₂/V_C degradation method using cudge fruit as raw material. The polysaccharides before and after degradation were analyzed for their physicochemical properties using high performance gel permeation chromatography and ion chromatography, and compared for their total antioxidant activity, reducing ability, DPPH radical scavenging rate and OH radical scavenging rate. Results: The suitable ratio of this cudge polysaccharide degradation by H₂O₂/V_C method was H₂O₂:V_C=1.5:1, and the five kinds of cudge polysaccharide ZGB, ZGC, ZGD, ZGE and ZGF (Mn 49.9, 30.5, 27.6, 25.9, and 28.9 kDa) were obtained. The structure did not change significantly after degradation by infrared spectrogram analysis. IC analysis showed that it was composed of rhamnose, arabinose, galactose, glucose, xylose galacturonic acid and a small amount of glucosamine hydrochloride and mannose. All the five kinds of polysaccharides with low molecular weight had antioxidant activity, which was positively correlated with its concentration. Among them, ZGD (H₂O₂:V_C=30:20 mmol/L) had the best antioxidant activity, compared with crude polysaccharide, its total antioxidant activity and reducing capacity increased by 42.7% and 10.8%, respectively, and the scavenging rate of ·OH increased by 56.3%, while the scavenging rate of DPPH· was not significantly enhanced, and the scavenging rate was 87.44%. Conclusion: After degradation, the antioxidant activity of polysaccharide ZGD is the best.