Optimization of polysaccharide extraction process from Polygonatum kingianum Collett & Hemsl. and analysis of in vitro antioxidant and hypoglycemic activities

【Objective】To optimize the extraction process of Polygonatum kingianum Collett & Hemsl. polysaccharide and analyze its in vitro antioxidant and hypoglycemic activities，with a view to providing reference basis for the large-scale development of Polygonatum kingianum Collett & Hemsl. products.【Method】Papain complex cellulase were added to the extract of Polygonatum kingianum Collett & Hemsl. in a certain proportion to extract Polygonatum kingianum Collett & Hemsl. polysaccharides in a single factor-response surface experiment，and optimize the optimal extraction conditions of Polygonatum kingianum Collett & Hemsl. polysaccharides in the solid-liquid ratio，pH，complex enzyme addition and the enzyme digestion temperature. At the same time，the in vitro antioxidant activity and hypoglycemic activity of Polygonatum kingianum Collett & Hemsl. polysaccharides obtained under these optimal extraction conditions were further evaluated.【Result】The optimal extraction process for the polysaccharide of Polygonatum kingianum Collett & Hemsl. was 1∶23（g/mL），pH 4.6，complex enzyme addition 14.5 g/L and enzyme digestion temperature 52 ℃，the extraction rate of polysaccharides of Polygonatum kingianum Collett & Hemsl. obtained under this condition was 22.27%，which was not significantly different from the theoretical value（22.31%）（P>0.05），and the influence of each factor on the polysaccharide yield was as follows：enzyme digestion temperature > pH > solid-liquid ratio > complex enzyme addition. The 4 factors had extremely significant effect on the polysaccharide extraction rate of Polygonatum kingianum Collett & Hemsl. （P<0.01）. The Polygonatum kingianum Collett & Hemsl. polysaccharides obtained by this method showed vital scavenging effects on 2，2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid（ABTS）cation radicals，1,1-diphenyl-2-picrylhydrazyl（DPPH）radicals，hydroxyl radicals，and superoxide anion radicals，with semi-inhibitory concentration（IC₅₀） values of 0.26，0.54，1.07，and 0.59 mg/mL，and showed obvious reducing iron ions capacity，with an IC₅₀ of 0.62 mg/mL. Using acarbose as a positive control，when the mass concentration was 1.2 mg/mL，the inhibition rates of α -glucosidase and α-amylase by Polygonatum kingianum Collett & Hemsl. polysaccharides were 35.65% and 49.83% respectively， which showed certain hypoglycemic ability.【Conclusion】The process optimized by single factor and response surface experiments can improve the extraction rate of Polygonatum kingianum Collett & Hemsl. polysaccharides，and the polysaccharides obtained have strong in vitro antioxidant and hypoglycemic activities.