Chemical Composition Of Auricularia Auricula Polysaccharides In Different Dehydration Methods And Their Effects On Antioxidation And Reversal Of Glucose And Lipid Metabolism Disorder

Auricularia auricula is a precious colloid fungus for both medicine and food.Auricularia auricula polysaccharide（AAPs）is its main nutritional component,which has many biological activities,such as antioxidation,anticoagulation,lowering blood sugar,lowering blood lipid,and so on.Dehydration is an important process for the preparation of natural polysaccharides.Different dehydration methods may cause irreversible changes in the structure of polysaccharides,resulting in significant changes in monosaccharide composition,molecular weight,and biological activity.In this paper,Auricularia auricula polysaccharides were conducted via different dehydration methods including freeze-dehydrated,hot-air dehydrated,infrared dried to obtain freeze-dehydrated Auricularia auricula polysaccharides（AAPs-F）,hot-air dehydrated Auricularia auricula polysaccharides（AAPs-H）,and infrared dehydrated Auricularia auricula polysaccharides（AAPs-I）.Detecting the ability to scavenge free radicals in vitro and antioxidant stress in vivo,exploring the regulation mechanism of antioxidant stress.The aim of this paper is to provide a scientific foundation for selecting appropriate dehydration methods to obtain AAPs with desired functionality which will expand its potential application in functional foods.The main results are as follows:1.Three kinds of AAPs（AAPs-H,AAPs-I,and AAPs-H）were obtained by hot-air dehydrated,infrared dehydrated,and freeze-dehydrated.Three kinds of AAPs were scanned by SEM and Fourier transform infrared spectroscopy,and the monosaccharide composition and molecular weight of monosaccharides were determined,The results showed that the surface microstructure of AAPS was different under the three dehydration methods.Infrared spectra showed that the three AAPs had a series of absorption peaks at 1000-1367 cm^-1,indicating that pyranose existed in the three AAPs;All the three AAPs have a weak peak at 828 cm^-1,indicating that they all existβ-Glycosidic bond.The molecular weights of the three polysaccharides are different.The molecular weights of AAPs-H are 1030.39 k Da and 171.68 k Da;The molecular weights of AAPs-I are 1003.81 k Da and 390.04 k Da;The relative molecular weight of AAPs-F is 406.77 k Da.The monosaccharide composition of the three AAPS is composed of mannose,glucuronic acid,glucose,galactose and xylose.The molar ratio of monosaccharides in AAPs-H is 12.00:1.80:1:2.53:7.01;AAPs-I is 12.34:2.04:1:2.52:7.01;AAPs-F is 13.73:0.98:1:2.87:8.32.2.The free radical scavenging ability of AAPs（AAPs-H,AAPs-I,and AAPs-H）in vitro was determined by colorimetry.The results showed that AAPs without dehydration and AAPs（AAPs-H,AAPs-I,and AAPs-F）treated by three different dehydration methods had good effects on the scavenging ability of DPPH radical and ABTS radicals,metal ion chelating power,and reducing power,and had an obvious concentration-dependent relationship.The antioxidant effect of AAPs-F and AAPs-H was better than that of AAPs-I in vitro.3.Using C.elegans as a model to study the protective effects of different dehydration methods of AAPs on oxidative damage induced by hydrogen peroxide and methyl viologen.The results showed that three different AAPs（AAPs-H,AAPs-I,and AAPs-F）could alleviate the oxidative damage of C.elegans and prolong the life span of oxidative stress worms,Among them,the AAPs-H of 0.8mg/m L could play a significant role in prolonging the life span of oxidative stress C.elegans induced by methyl viologen,and the AAPs-F of 0.8mg/m L could play a significant role on prolonging the life span of oxidative stress nematodes induced by hydrogen peroxide.The protective effects of different AAPs on methyl viologen-induced and hydrogen peroxide-induced injury were different,which indicated that the method of dehydration could affect the antioxidant stress of polysaccharides in vivo.4.Acridine orange（AO）staining was used to explore the protective effects of different AAPs on apoptosis of C.elegans induced by methyl viologen.C.elegans treated with different AAPs were subjected to acute stress with a high concentration of methyl viologen solution at 25℃for 1.5 h and observed by a fluorescence imaging system.The results showed that the apoptotic cells of C.elegans in the three AAPS treatment groups were significantly reduced compared with the negative group.and AAPs-F showed a more significant effect than AAPs-I and AAPs-H.RT-PCR showed that AAPs with different dehydration methods could up-regulate the expression of daf-16,sod-3,sir-2.1,and skn-1 genes in C.elegans under oxidative stress,among which AAPs-F shows the most significant effect.5.Streptozotocin（streptococci,STZ）was used to replicate the acute diabetic mouse model,and exploring the differences of antioxidant effect and the regulation of glucose metabolism disorders among these three AAPs.The results showed that the three AAPs could increase the level of glucagon like peptide-1（GLP-1）,reduce the degree of insulin resistance,alleviate the hyperglycemia state of mice,improve the oxidative stress damage caused by hyperglycemia,increase the activities of catalase（CAT）and superoxide dismutase（SOD）,increase the content of glutathione（GSH）and reduce the level of lipid peroxidation,It can regulate the activities of key enzymes of glucose metabolism（PEPCK,PK）and improve the disorder of glucose metabolism in mice.6.The Illumina Hi Seq sequencing platform was used to analyze the liver of STZ-induced diabetic mice fed by AAPs-F by transcriptome sequencing（RNA-seq）,and LC-MS and GC-MS were used to analyze the metabolomics of liver of STZ-induced diabetic mice.461 and 954 significantly different genes were found in the AAPs-F-L vs negative control and AAPs-L-M vs negative control,respectively,which were located on 231 and 290 KEGG pathways respectively,11 and 20differentially expressed genes related to the oxidation-reduction process were found respectively,7 and 6 differentially expressed genes related to glucose and lipid metabolism process were found respectively.99 and 16 significantly different metabolites were found in AAPs-F-L vs negative control and AAPs-F-M vs negative control,which were located on 21 and 7 KEGG pathways respectively.In summary,three dehydration methods were used to treat AAPs,and its structure,molecular weight and monosaccharide composition were characterized.The antioxidant activities of three kinds of AAPs in vivo and in vitro and their effects on glucose and lipid metabolism in diabetic mice were tested.The results showed that AAPs-F had good antioxidant activity in vivo and in vitro,and could improve the symptoms of hyperglycemia in diabetic mice.Its molecular mechanism was screened preliminarily.