Research On The Preparation And Hypoglycemic Activity Of Low Molecular Weight Polysaccharide From Cordyceps Militaris

The nutritional substance of Cordyceps militaris is extremely abundant.As the main active ingredient,Cordyceps polysaccharide draws great attention to the public as the result of strong biological activity and highly application.Over the years,it has focused on the research of biological activity of Cordyceps polysaccharide.But the Cordyceps polysaccharide has the high molecular weight and the poor water solubility and these characteristics can affect the utilization rate and biological activity of polysaccharide in vivo.So it is necessary to reduce the molecular weight and increase the solubility and the biological activity of polysaccharide.In this paper,the relationship between low molecular weight polysaccharide and Hypoglycemic activity have been discussed.The main methods and results are as followed:Through single factor experiment,the system to screen the a-glucosidase inhibitors in vitro was established:the enzyme activity of 1 U/mL,enzyme fluid dosage of 400 μL,the substrate concentration of 15 mmol/L,reaction time of 40 min,precise RSD of 0.3%,repetitive RSD of 0.5%.The crude polysaccharide was extracted by ethanol subsiding and sevage method from Cordyceps militaris.The sugar content of the crude polysaccharide was 37.9%by the analysis of Phenol sulfuric acid and DNS method.The crude polysaccharide was separated by SephadexG-100.The suger content of the purified polysaccharide was 83.1%.The molecular weight of the purified polysaccharide was 650 KDa by using high performance gel permeation chromatography(HPGPC).The degradation of the polysaccharide was determined by the inhibition rate ofα-glucosidase.The acid concentration,substrate concentration,degradation time,degradation temperature were analyzed by orthogonal test to obtain the low molecular weight polysaccharide.The results showed that the optimal conditions were the acid concentrate of 0.125 mol/L,the substrate concentration of 15 mg/mL,the reaction time of 0.5 h and the degradation temperature of 75℃.When the substrate concentration of low molecular weight polysaccharide was 0.25～1.75 mg/mL,the alpha glucosidase inhibition rate in vitro is better than the polysaccharide and the acarbose.The low molecular weight polysaccharide was isolated and purified by SephadexG-75.The purified low molecular weight polysaccharide was about 28 KDa.The specific rotation determination,IR,monosaccharide composition analysis,periodate oxidation and smith degradation,nuclear magnetic resonanee analysis,and Congo red test were used to analy the structure of low molecular weight polysaccharide.The results showed that the rotation of low molecular weight polysaccharides was+25°,and that it was mainly composed of rhamnose,xylose and glucose with the molar ratio of 1:2.19:6.73 and the linkage of 1→6,1→2 and 1→4.The hypoglycemic activity of low molecular weight polysaccharide in vivo was verified by the high blood glucose mice-model.The results showed that the low molecular weight polysaccharide had a significant effect on control blood glucose(p<0.01),and it could effectively alleviate diseases caused by high blood glucose.