Sulfated Modification, Composition And Antioxidant Activity Of Polysaccharides Of Liquid Cultured Inonotus Obliquus

Inonotus obliquus(I.obliquus) belongs to basidiomycotina, polypores, basidiomycetes genus. It is a rare edible and pharmaceutical fungus. Inonotus obliquus is a wood rotting fungus and mainly distributes in the north latitude 45o~50o, such as Europe, Asia and North America. It has a variety of chemical composition including polysaccharides, triterpene compound and so on and has very extensive application value. The polysaccharides of I.obliquus are a kind of important bioactive compounds. It has a variety of biological activity including immunomodulatory, antitumor, free radical oxidation resistance, hyperglycemic etc, on the other hand, has no poisonous effect on humans. However, the natural resources of I.bliquus are scarce and it is cost to extract the bioactive substances from natural fruitbody and disadvantageous for natural resources production. So in order to meet the increasing consumption demand, the exopolysaccharides(EPS) and endopolysaccharides(IPS) were produced by liquid submerged fermentation cultivation. The production and physicochemical properties of polysaccharides of I.bliquus can be affected by the submerged culture conditions. In this paper, we compared the sulfated modified of three different sources of polysaccharide 1) control medium 2) under the promoting of surfactant 3) under the stimulus of lignocellulose degradation.The biological activity of polysaccharides relates to its structure. The structure of polysaccharide modification means to modify the molecular structure of the polysaccharide by physical or chemical methods, in order to obtain different pharmacological properties and even create new biological activity of polysaccharide derivatives. Sulfated polysaccharide is a kind of polysaccharide on the hydroxyl containing sulfate radical, including various sulfated polysaccharide extracted from plants, sulfate acid derivatives of natural neutral polysaccharides and synthetic all different kinds of sulfated polysaccharide. Polysaccharides sulfuric acid modification will result in conformation changes which is the decisive factor for biological activity changes. Most the literature study shows that the biological activity of polysaccharides often enhanced and even may produce a new biological activity through sulfated modification. In the study, we researched polysaccharides of I.obliquus from three different medium, and compared their antioxidant activity and related pharmacological properties respectively, discussioned the structure-actiity relationship.The experimental results show that:1、The determination of sulfated modification conditionsThe modification condition was determined by using the EPS from the control medium. With the substitution degree as the degree, the conditions were determined by orthogonal experiments for the temperature 75℃, time 2.5h, ratio of 1:2.5.2 、 Sulfated modification impact on the physicochemical properties of polysaccharidesDuring the three different medium, lignocellulose-containing medium has the highest uronic acid content and polyphenol content of intracellular and extracellular with the content of 7.92%, 8.74 and 2.29%, 5.69%. At the same time, the lignocellulose-containing medium has the highest protein content and sugar content of extracellular with content of 36.28% and 25.77%. Tween 80-containing medium could promote sugar content and uronic acid content of intracellular and extracellular. The control medium has the highest protein content of intracellular, and the lignocellulose-containing medium could promote the content of extracellular protein, but reduce the content of intracellular protein.After three different sources of polysaccharides were modificated in the optimal sulfated medication conditions, the samples as sEPSct, sEPSws, sEPSt80, sIPSct, s IPSws, sIPSt80. The substitution degree of EPS was higher than IPS in the same modificated conditions. Furthermore, the chemical composition content of all the EPS and IPS were decreased.The average MWs and MNs of EPSws, EPSt80, sEPSws, and sEPSt80 were almost less half of those of EPSct and sEPSct. The MW/MN values of EPSct and sEPSct were much smaller than those of EPSt80, EPSws, sEPSt80, and sEPSws, and the values were closer to 1 which indicated they were more homogeneous.3、Sulfated modification impact on the structure of polysaccharideThe polysaccharides of I.obliquus were mainly composed of glucose, mannose, galactose and a small amount of xylose, arabinose and rhamnose. During the extracellular polysaccharides, lignocellulose-containing medium containing the highest mannose with the content of 32.6%,the following is control medium and Tween 80-containing medium with the content of 16.3% and 28.1%. During the intracellular polysaccharide, lignocellulose-containing medium and Tween 80-containing medium have higher levels of glucose with content of 65.3% and 65.8% respectively. On the other hand, the glucose of three different sources of culture medium of extracellular polysaccharides was higher after sulfated modification respectively.The molecular morphology of EPSct smaller and more homogeneous; EPSws have more cylindrical block shape and more smooth; futhermoer, EPSt80 molecules present acicular morphology and more intensive, however the molecular morphology of sEPSt80 more smooth and appeared more massive cylinder.4、Sulfated modification impact on the antioxidant activity of polysaccharideThe DPPH radical scavenging of polysaccharides with the order: sEPSws > sEPSt80 > EPSws > EPSt80 > sEPSct > EPSct. Furthermoer, for the intracellular polysaccharides have: sIPSws > sIPSt80 > IPSws > IPSt80 > sIPSct > IPSct. Moreover, the IC50 values of sulfated polysaccharides were lower than the corresponding native polysaccharides respectively, and the sEPSws has the minimum IC50 value with 1.65 mg/m L.These results indicate that under the stimulation of lignocellulose degradation and Tween 80 surfactants, the physicochemical properties and structure of polysaccharides of I.obliquus differs from that of control medium. More important is that the antioxidant activity of all the EPS and IPS were significantly increased after sulfated modication, furthermore, there are some structure-activity relationship between the antioxidant of polysaccharides and their physicochemical properties and structure.