| The Grifola frondosa,considered as a rare fungus riching in polysaccharides,proteins,mineral elements and other biologically active substances,had unique medicinal values and enjoyed the title of"North China Ginseng".At present,the G.frondosa had been widely artificially cultivated,however,a large amount of G.frondosa residue had been produced.In this project,the extraction conditions of G.frondosa residue polysaccharides（GRP）were optimized.Moreover,the monosaccharide composition,molecular weights and in vitro antioxidant capacities of GRP were processed,and the reparing effects of GRP against dextran sodium sulfate（DSS）-induced ulcerative colitis（UC）were investigated in mice.The results were listed as follows:（1）Optimization of GRP extraction.According to Plackett-Burman（PB）and response surface methodology（RSM）experiments,the optimal extraction conditions for GRP were extraction temperature of 91.94℃,pH of 7.83 and alcohol precipitation temperature of 8.25℃with the theoretically predicted yields of 4.14%.Experimentally,the extraction conditions were set as the extraction temperature of 92°C,pH of 8,and alcohol precipitation temperature of 8°C.Under the conditions,the theoretical yields of GRP was 4.12%,and the actual value was 4.13%,respectively.After deproteinization,depigmentation,dialysis and freeze-drying operations,the purified GRP was obtained.（2）Structural analysis of GRP.The high-performance gel-permeation chromatography（HPGPC）analysis showed that the molecular weight of GRP was 3.45×104Da,composed of mannose,ribose,rhamnose,glucuronic acid,galacturonic acid,glucose,and hemi lactose,xylose,arabinose,fucosidosewithamolarratioof4.67:0.67:5.08:1.97:2.88:12.52:7.40:7.70:6.00:2.52.The fourier transform infrared spectroscopy（FT-IR）analysis showed that GRP had a characteristic absorption peak of polysaccharides,and a characteristic peak near 1259cm-1,indicating that GRP contained uronic acid,a kind of pyranose withβ-type glycosidic bond.（3）The in vitro antioxidant capacities of GRP.The in vitro results showed that the reducing power of GRP was 0.90,and the scavenging rate of superoxide anion,hydroxyl and DPPH free radicals was 60.34±2.36%,78.92±2.19%and 82.21±2.32%,indicating that GRP had potential in vitro antioxidant capacities.（4）The repairing effect of GRP on injury of DSS-induced UC colon in mice.（1）After GRP intervention,the weight of mice was gained slightly,the water intaking was increased,and the fecal morphology was improved comparing with the UC mice.Moreover,when compared with that in the model group,the DAI score was icreased significantly.（2）The ulcers of mice in the model group had been appeared in the mucosal congestion abscess of the colon tissue with the dark brown tissues and local necrosis.After GRP intervention,the length of the colon was increased,which showed potentia degrees of apparent relief meanwhile.Meanwhile,the macroscopic score was also been reduced.（3）The hematoxylin-eosin staining（H&E）and pathological observation showed that GRP could reduce the infiltration of inflammatory cells and improve the mucosal damage.（4）GRP could significantly reduce the levels of tumor necrosis factor-α（TNF-α）,interleukin-6（IL-6）and myeloperoxidase（MPO）,thereby reducing the adverse effects of inflammation in mice.（5）The GRP（600mg/kg bw）could significantly increase the activities of superoxide dismutase（SOD）,glutathione peroxidase（GSH-Px）and catalase（CAT）on reducing the damage of the antioxidant defense system,decline the concentrations of nitric oxide（NO）and reactive oxygen species（ROS）on reducing free radicals damage to the body,and decrease the levels of malondialdehyde（MDA）and lipid peroxidation（LPO）on inhibiting the lipid peroxidation in colon tissue,respectively.The present results had indicated that GRP could repair the colonic tissue in DSS-induced colitis mice potentially,providing references for the in-depth study of GRP structure-activity relationship,and the development and application of natural drugs. |
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