Structure Characterization,Chemical Modification And Bioactivities Of Polysaccharide From Lachnum YM38

Lachnum was a kind of saprophytic fungi which could produce many active substances such as polysaccharides,pigments and polyphenols et al.A novel polysaccharide isolated from the Lachnum YM38 fermentation broth was studied,the basic structure characteristics,simulated digestion,chemical modification and bioactivities in vivo and in vitro of the polysaccharide were discussed.The main results were as follows:1)HPGPC,IC,GC-MS,FT-IR and NMR results showed that the molecular weight of LEP-1a was 5.69×10⁴ Da,which was mainly composed of galactose,glucose and mannose at the molar ratio of 9.4:14.6:76.9.The main linkage types of LEP-1a were proved to be（1→）,（1→3）,（1→4）and（1→2,6）linked mannose,（1→2）linked galactose and（1→2）linked glucose.In the simulated saliva-gastrointestinal digestion system in vitro,it was found that saliva had little effect on the digestion characteristics of LEP-1a.However,after gastrointestinal digestion,the reducing sugar contents of LEP-1a elevated apparently and its molecular weights decreased evidently,suggesting that LEP-1a could be partially degraded.Moreover,in vitro binding capacities,antioxidant activities,hypoglycemic and prebiotic activities of LEP-1a significantly increased after gastrointestinal digestion.2)ZnLEP-1a and SeLEP-1a were obtained by chemical modification of LEP-1a with zinc and selenium,respectively.The results showed that the zinc content in ZnLEP-1a was 0.69±0.03 mg/g,and the selenium content in SeLEP-1a was 206.99±9.85μg/g.SEM and AFM suggested that the morphology of LEP-1a was changed apparently after zinc and selenium modification.It was confirmed that ZnLEP-1a and SeLEP-1a were successfully modified by FT-IR and NMR.The FT-IR absorption peak of ZnLEP-1a shifted,and a new absorption vibration peak appeared in the FI-IR of SeLEP-1a.Proton signal of ZnLEP-1a was weakened in the ¹H NMR spectra,and the new peak of SeLEP-1a appeared at 62.62 ppm in the ¹³C NMR spectra,which was attributed to O-6substituted carbon.Compared with LEP-1a,ZnLEP-1a and SeLEP-1a had stronger antioxidant and antitumor activities in vitro.3)The cisplatin（CP）induced acute liver injury model was established and the hepatoprotective effects of LEP-1a and ZnLEP-1a was investigated.Results suggested that LEP-1a and ZnLEP-1a could significantly reduce liver index in and improve liver function as well as oxidative stress in mice.At the same time,it inhibited the expression of TNF-αand IL-1βin serum and reduced inflammatory cell infiltration in liver tissue.Therefore,LEP-1a and ZnLEP-1a could alleviate CP induced acute liver injury,which was related to inhibit oxidative stress and inflammation.4)To discuss the renal protective effects and the mechanism of LEP-1a and SeLEP-1a,CP was used to establish acute kidney model.The results demonstrated that LEP-1a and SeLEP-1a pretreatment could effectively reverse the decrease of renal index and the increase of CRE and BUN levels in serum induced by cisplatin.LEP-1a and SeLEP-1a pretreatment could also improve renal oxidative stress by restoring antioxidant enzyme activity and GSH content.In addition,compared with the model group,LEP-1a and SeLEP-1a significantly reduce the contents of inflammatory cytokines IL-1β,IL-6,TNF-αand KIM-1.Immunohistochemical results showed that LEP-1a and SeLEP-1a could inhibit the release of COX-2 and i NOS and increase the expression of Nrf2 and HO-1.At the same time,the results of PCR indicated that SeLEP-1a could significantly inhibit the m RNA expression levels of TLR4,NF-κB p65 and IκBαrespectively.What’s more,western blot analysis signified that LEP-1a and SeLEP-1a significantly downregulated the protein expression levels of Bax and cleaved caspase-3,upregulated p-PI3K,p-Akt and Bcl-2 protein expression levels in kidney.In summary,LEP-1a and SeLEP-1a pretreatment could improve CP induced acute kidney injury by regulating oxidative stress response,NF-κB mediated inflammation and PI3K/Akt mediated apoptosis signaling pathway.