Studyon Preparation Techniques Of Bioactive Polysaccharide From Cordyceps Militaris

Cordyceps militaris,which is also called “Bei DongChongXiaCao” in China,has many biological and pharmacological activities.One of the most important functional compounds of C.militaris is polysaccharide which is reported to possess potential antioxidation.The optimum medium nutritional components(carbon source,nitrogen source and the mineral elements)were determined on the antioxidant ability for DPPH radical and reducing power of polysaccharide.The optimum values of the tested variables for the production of bioactive exopolysaccharide(CMP)by C.militaris in submerged culture were 20g/L mannose,15 g/L peptone,2 g/L yeas extract,5 g/L NaH2PO4,1 g/LMgSO4·7H2O.The scavenging effect of CMP on the DPPH radicals could reach 97.51% at the concentration of 1.2 mg/mL.And at the high doses of 6.0mg/mL,the reducing power of CMPwas 1.764.CMP-1 and CMP-2 were obtained by preliminary separation and purfication of CMP.The protein content and uronic acid content of CMP were 32.6% and 1.71%,while CMP-1 and CMP-2 barely contained any protein or uronic acid.The results were according with the data acquired from Ultraviolet spectrum and the HPLC chromatograms of polysaccharides.The molecular weight of CMP,CMP-1 and CMP-2 were 15705 Da and 5998 Da,7130 Da,8175 Da,respectively.It demonstratedthat both CMP-1 and CMP-2 are a kind of new type polysaccharide with low molecular weight.CMP was composed of mannose,rhamnose,glucuronic acid,galacturonic acid,glucose and galactose.CMP-1 and CMP-2 had the same monosaccharide compositions except glucuronic acid and galacturonic acid.From the Infrared spectrum of samples we can see that they all had the characteristic absorption peaks of polysaccharide,we also can deduce that polysaccharides contain pyranose.Both CMP-1 and CMP-2 had outstanding bioactivity,and the antioxidant ability of acidic polysaccharide(CMP-2)was higher than that of neutral polysaccharide(CMP-1).The effects of deproteinization and drying methods on the antioxidant activities of C.militaris polysaccharide were evaluated on the basis of assay for DPPH radical,hydroxyl radical,ABTS radical scavenging ability and reducing power.The results showed there was no significant difference on antioxidant capacity between crude polysaccharide(CMP)and polysaccharides deproteinized by sevag method(CMP-D-S)and enzymatic method(CMP-D-E).However,drying methods influenced the antioxidant activities of C.militaris polysaccharide.On the whole,polysaccharide obtained by freeze drying(CMP-F)displayed the strongest antioxidant abilities than that obtained by hot air drying(CMP-H)and spray drying(CMP-S).As a result,C.militaris polysaccharide is a natural antioxidant and freeze drying is a recommendable method for polysaccharide dehydrating and other antioxidants production for food industry.The water content of CMP-H,CMP-F and CMP-S were all less than 10%,and the protein content of them were 29.3%、31.4%、30.6%,respectively.The uronic acid content of CMP-H,CMP-F and CMP-S were all very low.The molecular weights of polysaccharides were about 13000 Da and 5000 Da.The main monosaccharide compositions of CMP-H,CMP-F and CMP-S were same(mannose and glucose),while the molecular ratios of compositions of each polysaccharide were different.There also had much difference on scanning election microscope photographs of polysaccharides.Different drying methods have an appreciable effect on the antioxidant properties of polysaccharides.This study makes the production of Cordyceps militaris polysaccharide in a more targeted way.These data supplied theoretical foundation for the production of C.militaris bioactive polysaccharide,and they also played a good role in the product development about Cordyceps militaris.