Extraction, Characterisation And Antioxidant Activities Of Polysaccharide From Pleurotus Ostreatus

Pleurotus ostreatus is well known as an edible fungus which has highly nutritious function, and are planted widely in China. P. ostreatus are rich in nutrients, polysaccharides of P.ostreatus are main function components. In recent years, the polysaccharides from P.ostreatus were paid much more close attentions due to many kinds of biological activities such as antioxidant, anti-inflammatory, antitumor, anti-promotion properties and so on.In this thesis, the materials were the fruiting bodies of P.leurotus. Orthogonal design method was set up to find optimization of the extracting conditions for polysaccharides from P.ostreatus, which could improve the rate of polysaccharide. Then polysaccharides extracted from the P.ostreatus were isolated and purified, in addition, the structural characteristics of the purified polysaccharides were detected and explained. Finally, the activities of polysaccharides from P.ostreatus on repairing the damage of mesangial cells induced by high glucose and scavenging DPPH radicals, superoxide radicals and hydroxyl radicals were researched. The experimental results were given as follows:1. The extraction processes of crude polysaccharides from P.ostreatus were studied. Orthogonal design method was used to optimize the extracting conditions in order to improve the extraction efficiency and quality of polysaccharides. The final optimization extracting conditions were as follows:the ratio of material to water1:30, leaching time3h, leaching temperature60℃, ethyl alcohol concentration75%. The yield of crude polysaccharides was5.7%.2. PSPO was fractionated and purified by DEAE-52anion-exchange chromatography. The column was eluted with distilled water, and PSPO-1and PSPO-2were obtained, followed by0to1mol L-1linear gradient of NaCl, and PSPO-3and PSPO-4were obtained. The two main fractions were further purified by gel permeation chromatography on a superdex75column performed on AKTA basic system, two homogeneous polysaccharides, PSPO-1a and PSPO-4a, were obtained.3. Physicochemical properties of the polysaccharides were determined by spectroscopic and HPLC analysis. PSPO-1a was composed of mannose, glucose, galactose, xylose and rhamnose with a molar ratio of2.47:0.91:1.0:1.66:3.87. PSPO-4a was composed of only three monosaccharides:rhamnose, mannose and galactose with a molar ratio of0.92:2.69:1.0. The average molecular weight of PSPO-1a and PSPO-4a were estimated to be1.8×104Da and1.1×106Da respectively.4. Several in vivo studies revealed that PSPOs were potential free-radical scavengers. PSPO-la showed a better scavenging ability (IC501.43mg/mL) than PSPO-4a (IC502.3mg/mL) against the DPPH radical. The IC50values of PSPO-1a and PSPO-4a against the the superoxide radicals were2.0mg/mL and4.8mg/mL respectively. The IC50values of PSPO-1a and PSPO-4a against the the hydroxyl radicals were6.1mg/mL and7.0mg/mL respectively.5. Two polysaccharides were assayed for antiproliferative and antioxidant effects on cultured mouse mesangial cells. The results showed that PSPOs could significantly inhibit the proliferation of mesangial cells induced by high glucose; improve SOD, GSH-Px activity and reduce MDA content at the concentration of40-20ug/mL. In addition, PSPO-la and PSPO-4a could also reduce the production of TGF-β1, FN and IV-C in mesangial cells under oxidative stress, suggesting that PSPOs have potential clinical value and application prospect as a therapeutic agent for diabetes and diabetic complications.