Study On Isolation,Purification,Physicochemical Properties And Hypoglycemic Activity Of Onchidium Struma Polysaccharides

In recent years,marine shellfish polysaccharides have shown a remarkable application prospect in anti-tumor,hypoglycemic improving body immunity and so on.As a kind of marine shellfish,Onchidium struma has a long history of consumption and has the functions of nourishing and strengthening the liver and kidney,and treating asthma and rheumatism.Its polysaccharides content is about 25%.Onchidium struma polysaccharides(OSP)medicinal value is high.At present,it is mainly used in food rough processing,while its active components are less studied.Here,OSP with medicinal value is extracted efficiently,and its activity in hypoglycemia is studied,which provides a useful reference for the development of hypoglycemic products and further expands the field of high-value utilization of Onchidium struma.In this paper,OSP were extracted and purified,then its physicochemical properties,fundamental chemical structure and hypoglycemic effect were investigated.The research contents and results are presented as follows:(1)Extraction of OSP by ultrasonic assisted method.Based on the single factor experiment,the response surface method was used to optimize the extraction process.The results show that the optimum extraction conditions were as follows:extraction temperature of 90?,extraction time of 76 min,ultrasonic power of 753 W.Highest yield under these conditions,the average yield of OSP was 10.09%±1.05%.The extraction temperature has the greatest effects on yield,followed by ultrasonic power;the interaction between ultrasonic power and time,time and temperature has significant effects on polysaccharide yield.According to the comprehensive analysis of protein removal rate and polysaccharide retention rate of three methods,we compared the Sevage reagent method,enzyme method and enzyme-Sevage method,finding that enzyme-Sevage method had the best protein removal rate,and the protein removal rate was 98.52%,the retention rate of polysaccharides was 96.50%.(2)The separation and purification of crude OSP was conducted by column chromatography.The crude OSP were preliminarily separated by DEAE Sepharose Fast Flow anion exchange column to obtain fractions of OSP1 and OSP2,and were further purified by Sephacryl S-300 size exclusion column to obtain the fractions of OSP1-1and OSP2-1.The OSP and its purified components were identified by physicochemical properties and structures.The results showed that the average molecular weight of OSP was 1.34×10~6 Da.The OSP1-1 has the highest polysaccharide content,which was 52.51%;the OSP2-1 has the lowest protein content,which was 0.92%.The total phenolic content of the three polysaccharides was lower.Among them,the glyoxylic acid content of OSP,which was 4.16%,was the highest,the sulfuric acid group content of OSP and OSP2-1 was higher than that of OSP1-1,which was 0.91%.The OSP and its purified components have characteristic UV line trend and infrared absorption peak.The crude OSP were composed of fucose,rhamnose,glucose,galacturonic acid,glucuronic acid and mannose;the OSP1-1 rhamnose,galacturonic acid and fucose;and the OSP2-1 mannose,glucuronic acid,galacturonic acid and fucose.(3)In vitro and in vivo experiments were conducted to investigate the hypoglycemic activity of crude OSP.First,the experiments of inhibition of?-glucosidase activity were conducted to investigate the in vitro hypoglycemic ability of crude OSP,indicated that the inhibition rate of OSP on?-glucosidase at the concentration of 40?g/mL and 50?g/mL are 72.8%±5.0%and 82.2%±3.3%,respectively,slightly higher than acarbose.Second,mice were fed with high glucose and high fat diet and injected the streptozotocin(STZ)in abdominis,then the model of type 2 diabetic rat was established.Compared with metformin hydrochloride,the hypoglycemic effect of crude OSP on type 2 diabetic mice was investigated.The results showed that the diabetic mice were significantly increased in body weight,decreased in fasting blood glucose value and improved in glucose tolerance,after treated with crude OSP.At the same time,the serum total bile acid content in diabetic mice was significantly decreased;the TC,TG,LDL-C content in serum and liver was decreased,while the HDL-C content was increased;the insulin sensitivity index was enhanced;the inflammation of liver,jejunum,cecum,islet and other tissues in vivo was improved.