Study On Extraction,Structure Characterization And Biological Activities Of Oligosaccharides From Auricularia Heimuer

Auricularia heimuer is a traditional medicinal and food fungus in China.Studies have shown that Auricularia heimuer polysaccharide is one of the important biologically active components of Auricularia heimuer.It has multiple biological activities such as anti-oxidation,lowering blood sugar,lowering blood lipids and preventing radiation.However,the larger molecular weight and viscosity make the preparation standardization and structure research of Auricularia heimuer polysaccharides difficult.By hydrolyzing Auricularia heimuer polysaccharides to obtain oligosaccharide fragments,to reduce molecular weight and viscosity,and to characterize the structure and biological functions of Auricularia heimuer oligosaccharides,it will provide new theoretical and experimental evidence for the development and utilization of Auricularia heimuer.In order to establish a method for the preparation and separation and purification of Auricularia heimuer oligosaccharides,this study used Auricularia heimuer in Heilongjiang area as raw material,and used the pretreatment method of adding lactic acid bacteria after heat explosion to obtain Auricularia heimuer fermentation puree.Crude Auricularia heimuer polysaccharide（CAHP）was extracted from the fermented puree of Auricularia heimuer by hot water immersion method.Furthermore,this study used a combination of chemical oxidative degradation and physical degradation to hydrolyze the crude polysaccharide CAHP of Auricularia heimuer.By optimizing the conditions of H₂O₂ concentration,ultrasonic power and oxidation time,a fast and efficient CAHP degradation method was established.The degradation products were further subjected to anion exchange and gel exclusion chromatography to separate Auricularia heimuer oligosaccharide 1（AHO1）,with a yield of about 30%.Monosaccharide composition analysis results show that CAHP is composed of five monosaccharides,mannose,glucuronic acid,glucose,xylose and galactose,and the corresponding molar ratio is 1:0.22:0.12:0.12:0.01.AHO1 is composed of six monosaccharides:mannose,glucuronic acid,glucose,xylose,galactose and fucose,with a molar ratio of1:0.24:0.12:0.12:0.02:0.02.The structures of CAHP and AHO1 were characterized by high-resolution mass spectrometry,infrared spectroscopy,and proton nuclear magnetic resonance spectroscopy.The analysis of the spectrum proved that CAHP is a heteropolysaccharide with two configurations ofα-glycosidic bond andβ-glycosidic bond.AHO1 is an oligosaccharide with a degree of polymerization of 2-10 connected byα-glycosidic bonds.This study also conducted a preliminary analysis of the biological activity of AHO1,Auricularia heimuer oligosaccharide.AHO1 has antibacterial activity similar to ampicillin against Escherichia coli DH5αand Staphylococcus aureus ATCC6538.At the same time,AHO1 can significantly inhibit the growth of ampicillin-resistant genetically engineered bacteria DH5α/p GEX-6P-1,suggesting that the antibacterial mechanism of AHO1 is different from antibiotics.The results of in vitro antioxidant activity analysis show that AHO1 can effectively scavenge ABTS and DPPH free radicals.By establishing a H₂O₂-induced Hep G2 cell oxidative stress damage model,this study analyzed the cellular antioxidant activity of AHO1.The results showed that AHO1pretreatment has a good protective effect on H₂O₂ induced oxidative stress damage in Hep G2cells.In this study,we obtained the extraction method of low-polymerization Auricularia heimuer oligosaccharide AHO1,and preliminary explored the structure and biological activity of AHO1,which provided a new method and experimental basis for the research and further commercial application of low molecular weight Auricularia heimuer oligosaccharide.