| Auricularia auricula belongs to Fungi,Basidiomycota,Agaricomycetes,also known as fungus,cloud ear fungus and light black fungus,it is widely distributed within China.According to Food Composition Table,Auricularia auricula has high nutritional values.It is also a kind of traditional Chinese medicine.In the first medicine book of China,it was reported to be effective in curing some women diseases.Modern research results showed that it can reduce blood fats levels,scavenge free radicals,and has hypoglycemic and anti-cancer effects.In this study,we selected dry Auricularia auricula as raw material,and its water-extracted polysaccharide was studied to elucidate the preparation methods,physical and chemical properties,structural characteristics and in vitro hypoglycemic activities.The main results are as follows:(1)The preparation method of Auricularia auricula polysaccharide was established by comparing the contents and yields of Auricularia auricula polysaccharides obtained through different extraction methods,and the following preparation method was chosen: soak the Auricularia auricula powder in distilled water of p H 4.5 and 50 °C at the ratio of 1:25(g: m L)for 60 min,stir the mixture from time to time,add cellulose enzyme at the amount of 1.5% of raw material weight,heat the mixture under ultrasound for 80 min,heat to 100 °C for 10 min,extract polysaccharide at 80 °C for 2 h,filter,concentrate the filtrate,add 95% ethanol at the volume four times that of the filtrate,precipitate overnight,dissolve the precipitation distilled water and freeze drying.The obtained product was named as AAP1.Its sugar content was 85.93%,and the yield was 1.55%.(2)The physicochemical properties of Auricularia auricula polysaccharide were studied:The purity test results showed that the distribution of molecular weight of AAP1 was wide,and a great number of glucose(48.43%),mannose(16.98%),xylose(12.90%),as well as a small amount of galactose.were found in AAP1,which proved it's not pure.The content of protein in AAP1 was low(2.24%),the sum of all analyzed fractions in the sample was close to 90%,which proved that AAP1 was a kind of crude polysaccharide and needed further purification.(3)The structure of graded polysaccharide from Auricularia auricula was analyzed:AAP1-20 and AAP1-60 were obtained after treated by deproteinization,decolorization and isopropanol fractionation.The results of their basic physical and chemical property tests showed that although deproteinization led to the loss of polysaccharide in the sample,the total sugar content of AAP1-20 and AAP1-60 were still as high as 80.19% and 83.63%,respectively,and their protein contents were 1.06% and 0.82%,respectively.The purity test results showed that the distribution of molecular weight of AAP1-20 and AAP1-60 were concentrated,and the molecular weight of AAP1-60 was smaller than that of AAP1-20.AAP1-20 consisted only of glucose(77.82%),while AAP1-60 contained 4 kinds of monosaccharides,mainly mannose(51.91%)and xylose(43.62%),and a small amount of glucose(6.17%)and galactose(2.51%).Methylation analysis result showed that the major residues of AAP1-20 included 1,4,6-linked Glcp,1,3,6-linked Glcp,1,6-linked Glcp and T-linked Glcp,of which 1,3,6-linked Glcp content was the highest;the major residues of AAP1-60 included T-linked Galp,1,3-linked Xylp,1,4,6-linked Manp,1,4-linked Manp and 1,6-linked Glcp,of which 1,4-linked Manp content was the highest.The two samples were both highly branched.(4)The inhibitory effects of Auricularia auricula polysaccharide on hyperglycemia-related enzymes were determined:The in vitro inhibitory effects of Auricularia auricula raw material and AAP1 on xanthine oxidase and ?-glucosidase were studied.The results showed that the inhibition rate was positively correlated with the concentration of samples in a certain range,which proved its inhibitory effect on hyperglycemia-related enzymes. |
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