| Pleurotus ostreatus(Jacq.)P.Kumm is an eatable mushroom with the pharmacological benefits,because of its content of metabolites,basically polysaccharides.It has low calorie and no cholesterol,so it has certain medicinal value.The current research project was designed with the objective to find out the physicochemical properties of polysaccharides in oyster mushroom and to determine the antioxidant activity of polysaccharides.Five polysaccharides(OM-1,OM-2,OM-3,OM-4 and OM-5)were extracted from P.ostreatus using normal temperature water,dilute alkali(0.125 mol/L NaOH),concentrated alkali(1.25 mol/L NaOH),hot water and high pressure extraction and their physicochemical properties,structure and bioactivities were studied.The results can provide data for the development and application of P.ostreatus polysaccharide.The chemical composition analysis exhibited that the five polysaccharides contained certain amount of sugar,protein and uronic acid.The total sugar content of OM-1,OM-2,OM-3,OM-4 and OM-5 was 23.85%,48.51%,52.48%,68.66%and 86.76%respectively,the protein content was 5.42%,4.35%,4.26%,2.34%and 1.29%respectively,and the uronic acid content was 2.15%,3.54%,2.20%,1.25%and 0.93%respectively,But the proportion of different polysaccharides was different.In XRD analysis,there was a weak diffraction peak for each polysaccharide with different intensity was recorded when the 20 was nearly 47°,which was indicating the presence of both the amorphous nature and crystalline nature of the different polysaccharides.The SEM analysis results showed that the surface morphology of polysaccharides obtained by different methods was different.The structure of alkali extracted polysaccharides was damaged by alkali,and the surface morphology showed irregular block or sheet structure.In DSC analysis at 231.9?,304.6? and 300.1?,an exothermal valley appeared,respectively for OM-1,OM-2 and OM-3 in the DSC curve.While for OM-1 there was an endothermal peak at 246.9?.Thermogravimetric analysis(TGA,DSC)showed that the polysaccharides had good thermal stability.The FT-IR spectrum showed a broad peak around 3400cm-1 for hydroxyl,bunches extending vibrations;the top around 2900 cm-1 showed retention for C-H extending vibrations;the band around 1735 cm-1 showed assimilation for carboxyl gatherings extending vibrations,which can be utilized to decide the presence of uronic corrosive;a top around 1650cm-1 was happened because of the related water.The portrayal of the divisions by FT-IR spectra investigation showed average ingestion pinnacles of polysaccharides.The structure of OM-4 was analyzed by nuclear magnetic resonance(NMR).The results showed that the main chain of OM-4 was composed of ?3)-?-D-Glcp-(1?,?3)-?-D-Galp-(1? and the branched chain ?-D-Man(1? connected to the ? 3)?-D-Galp-(1?position)of the main chain through O-6.The biological activity analysis showed that the scavenging ability of OM-1,OM-2,OM-3,OM-4 and OM-5 polysaccharides on DPPH free radicals,hydroxyl free radicals and ABTS free radicals increased with the concentration of polysaccharides.When the concentration was 5 mg/mL,the DPPH free radical scavenging ability of the five components was 74.28%,54.97%,75.97%,82.77%and 70.88%respectively,the scavenging ability of ABTS free radicals was 88.38%,75.34%,92.91%,81.37%and 92.17%respectively and the scavenging capacity for hydroxyl radicals was 70.41%,64.22%,78.29%,67.84%,77.50%,respectively.Biochemical analysis confirmed that purified fraction OM-1 has strong free radical scavenging activity against DPPH,hydroxyl and ABTS free radical.The results of immunomodulatory activity analysis showed that the five components could promote the proliferation of mouse macrophages RAW 264.7,stimulate macrophages to produce NO,enhance the phagocytic ability of macrophages and had good immunomodulatory activity.The results revealed the polysaccharide's important role as potential natural antioxidant agents during the investigation and application of bioactive polysaccharides.The overall study suggested that Pleurotus ostreatus polysaccharide could be used as a potential natural antioxidant drug resource and has value for further scientific research in the food and pharmaceutical industry.Further studies are now in progress to gain more insight into its structures and identify other potential biological activities of these novel Pleurotus ostreatus derived polysaccharides. |
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