Study on Extraction Technology and Pharmacological Activities of Polysaccharide from Ziziphus jujube

Polysaccharide from Ziziphus jujube Mill. (ZJP) was extracted by ultrasound-assisted extraction. Taking the extraction rate as the evaluation index, the extraction process of polysaccharide was optimized by Design-Expert8.0 and orthogonal experiment on the basis of single-factor test. Subsequently, DPPH free radical and hydroxyl free radical scavenging abilities were used as indicators to evaluate the antioxidant effect of polysaccharides, and the inhibitory rates of α-amylase and α-glucosidase were used as indicators to prove that jujube polysaccharides had the potential of reducing blood sugar. Finally, an external model was established to explore its hypoglycemic mechanism. The optimum parameters were as follows: ultrasonic time of 40 min, solid-liquid ratio of 1:20, ultrasonic power of 80 W, water-bath incubation time of 30 min. Under these conditions the extraction rate of ZJP was 6.58%, which was consistent with the theoretical prediction value of 6.71%. Moreover, the antioxidant activity of ZJP was determined by DPPH free radical and hydroxyl free radical scavenging system and iron-reducing power. In addition, when the polysaccharide concentration reached 14 mg/mL, the inhibition rate of α-glucosidase was 51.56%, and when the concentration was 4 mg/mL, the inhibition rate of α-amylase was 28.43%, respectively, confirming that jujube polysaccharide had obvious hypoglycemic activity. On this basis, the insulin resistance HepG2 cell model was used to detect the glucose consumption effect of different concentrations of jujube polysaccharides by glucose kit and MTT method. The results showed that when the concentration of the drug was 1.0 mg/mL, the cell's consumption of glucose was the largest, GT/MTT reached 154.2% of the model group. Western blotting was used to detect the protein expression level of PI3K/Akt pathway in insulin-resistant HepG2 cells, and it was determined that ZJP could alleviate insulin resistance and exert cytoprotective effect by activating PI3K/Akt pathway. In summary, the extraction method of jujube polysaccharide was optimized, and it was confirmed that jujube polysaccharide had anti-oxidant activity and hypoglycemic activity in vitro, and could be used as a potential anti-oxidant or functional food with a homology of medicine and food.