The Radioprotective Effect Of Sulfated Auricularia Auricula Polysaccharide Degraded By High Pressure Homogenization

Auricularia auricula polysaccharide is a kind of natural edible mushroom polysaccharides and possesses a large variety of biological fuctions. However, the wide applications of Auricularia auricula polysaccharide are restricted, because Auricularia auricula is a kind of gelatinous fungi, in which the polysaccharide is difficult to spread out and can’t give full play to the biological fuctions for large molecular weight and poor water solubility. The cell walls of Auricularia auricula can be broken largely in favor of the dissolution of polysaccharide when high pressure homogenization is used to extract Auricularia auricula polysaccharide. Sulfation modification can change the type, number and position of substituents in polysaccharide, so that the physicochemical properties and biological activity change as well. All of these offer the possibility for the wide applications of Auricularia auricula polysaccharide.In this study, response surface methodology was used to optimize the high pressure homogenization process of polysaccharide from Auricularia auricula by investigating polysaccharide yield as a function of homogenization time, homogenization pressure and soild to solvent ratio and had gotten the optimum conditions. The optimized conditions were homogenization time 25 min, homogenization pressure 28 MPa, and solid to solvent ratio 1:86 g/mL. Under these conditions, the polysaccharide yield was 46.85%. Compared with the polysaccharide extracted by atmospheric pressure, high pressure homogenization can degrade macromolecular polysaccharide into small molecules and enhance the antioxidant activity of the polysaccharide by viscosity-average molecular weight determination and in vitro antioxidant study. Four fractions（HAAP20%、HAAP40%、HAAP60%、HAAP80%） were obtained after the fractionation of polysaccharide by ethanol. The bioactivity results in vitro showed that the antioxidant activity of HAAP80% was the best.Sulfation modification of HAAP80% was achieved by concentrated sulfuric acid method with the degree of sulfation as a fuction of reaction time, the volume of H2SO4 and the dosage of（NH4）2SO4. After using response surface methodology to optimize the sulfation process, the optimum conditions gotten were reaction time 0.9 h, the volume of H2SO4 8.0 m L and the dosage of（NH4）2SO4 130 mg.Under these conditions, the degree of sulfation was 0.595. The FT-IR spectra indicated that sulfation modification of Auricularia auricula polysaccharide was successful, because the FT-IR of sulfated Auricularia auricula polysaccharid（SHAAP） exhibited the typical signals of polysaccharides and the characteristic absorption peak of sulfate groups in the fingerprint region were enhanced significantly; According to UV spectrum, SHAAP didn’t contain nucleic acids and proteins; It was proved that the molecular size of SHAAP is uniform by GPC; Congo red experiment showed that SHAAP had stable triplex conformation; The analysis of monosaccharide composition showed that SHAAP was composed of D-glucose and D-mannose with the molar ratio of 1:1.69; The result of periodate oxidation indicated that the glycosidic bonds of 1�',1�'6,1�'2 and 1�'2,6 might exist; Smith degradation showed that SHAAP contained the glycosidic bonds of 1�'3, which couldn’t be oxidized by sodium periodate.The radioprotection effects of SHAAP was studied by establishing ⁶⁰Co-γ radiation damage model in mice. Results indicated that SHAAP could effectively improve the radiation-induced oxidative damage mainly through three ways. Firstly, SHAAP could significantly enhance the immune activity by increasing the organ index, enhancing the phagocytic activity of monocyte and promoting lymphocyte proliferation. Secondly, SHAAP could increase SOD activity, CAT activity and GSH level and decrease MDA level, so the radioprotection effects of SHAAP might be a consequence of free radical scavenging effect, promoted antioxidant activity and inhibitory action on lipid peroxidation.Thirdly, SHAAP offered significant protection to DNA and chromosomes against radiation damage by reducing micronuclei formation and increase DNA content in bone marrow cells. Compared with male mice, female mice had a stronger anti-radiation effect.