| In this paper, using Pleurotus eryngii as raw material, by use of ethanol, water and dilute alkali extraction, successively. Ethanol extracts, water-extracted crude polysaccharide and alkali-extracted crude polysaccharide were obtained, respectively. Firstly, ethanol extract was by solvent extraction, the yield of extract component was calculated, and the antioxidant activity of each component was compared study; Secondly, alkali-extracted crude polysaccharide was fractionated by anion-exchange and gel-permeation chromatography, obtaining a novel water-soluble composition termed PEAP-1. Its physicochemical properties, molecular structure and morphological were investigated by a combination of chemical and instrumental analysis approaches, including methylation analysis, partial acid hydrolysis, periodate oxidation, Smith degradation, HPLC, atomic force microscopy (AFM), infrared radiation (IR), gas chromatography (GC), ultraviolet spectroscopy (UV), scanning electron microscopy (SEM), nuclear magnetic resonance spectroscopy (NMR) and gas chromatography-mass spectrometry (GC-MS) in addition, also studied its DPPH free radical and hydroxyl free radical scavenging activities; Lastly, alkali-extracted crude polysaccharide was modified with four kinds of chemical methods. Respectively, sulfation, acetylation, phosphorylation, carboxymethylation, obtain the four components of the derivatized polysaccharide. And antioxidant activity of each component was compared study before and after the modification, to reveal the structure-activity relationship of antioxidant function and molecular structure of the alkali-extracted polysaccharide from Pleurotus Eryngii. The results are as follows:1. Alcohol extract and its solvent extraction components research results show that, the yield of chloroform extracted components, ethyl acetate extracted components, n-butanol extracted components and residual aqueous phase components were6.79%of9.2%,2.2%and78.35%, respectively. Antioxidation experiments showed that ethanol extract of each extract component, the strongest antioxidant capacity of the aqueous phase components. 2. The results of HPLC and GC analysis indicated that PEAP-1was a homogeneous polysaccharide whose average molecular weight is450kDa and monoaccharide is composed of Glu and Gal at a molar ratio of16.9:0.37. Moreover, the peak near832cm-1and919cm-1suggested the presence of pyranose ring in PEAP-1from the infrared spectroscopy. The Congo red test showed that PEAP-1has helix structure when contact with Congo-red. UV results indicated that the absence of protein, nucleic acid and pigment in this polysaccharide. On the basis of the partial acid hydrolysis, periodate oxidation, Smith degradation, methylation analysis, NMR spectroscopy and GC-MS results, the backbone of PEAP-1was composed of1,3-β-linked Glc, and the side chains of1,6-a-linked Gal were attached to the backbone by C-6of1,3-β-linked Glc residues:The free radical scavenging activity assay results showed that PEAP-1has some radical scavenging activity.3. AFM analysis showed, PEAP-1molecule is a random linear chain and multi-branched structure, the height of each single molecular strand in0.13nm-1.2nm. SEM showed that, PEAP-1presents the appearance of a flake, rods and mesh three kinds of morphology.4. Alkali-extracted crude polysaccharide was modified with four chemical methods, identified by infrared spectroscopy, the results showed that these four were chemically modified derivative of the successful. Antioxidation experiments showed that after modifying the activity of polysaccharides have a corresponding improvement, sulfated and phosphorylation polysaccharide activity is preferably. Of which, the total reducing power and DPPH radical scavenging activity of sulfated polysaccharides strongest, however, the hydroxyl radical scavenging activity of phosphorylation polysaccharides strongest. This shows that the enhanced antioxidant activity of polysaccharides may be due to changes in its molecular structure to achieve. |
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