Preparation And Antioxidant Activity Of Pumpkin Polysaccharide And Its Derivatives

Pumpkin polysaccharide is a kind of brown powder,which is an effective component with special biological activity in pumpkin?Cucurbita moschata?,and has the effect of enhancing immunity and anti-oxidation.It can also remove various free radicals generated by the body during metabolism,including superoxide anion radical?O₂^-·?,hydroxyl radical?·OH?and its active derivative?H₂O₂?.In this paper,the pumpkins purchased from the local vegetable market were used as raw materials to systematically study the extraction,separation,purification,derivatization,structural analysis and antioxidant activity of pumpkin polysaccharides.The specific contents are as follows:1.Considering the experimental conditions and facilities,the pumpkin polysaccharide was extracted by hot water extraction method.Then the protein in polysaccharide was removed by Sevage method.Finally,pumpkin polysaccharide?P?was obtained by dialysis and constant temperature drying.The content of polysaccharide determined by phenol-sulfuric acid method can reach 81.0%,which indicates that hot water extraction method and Sevage method are feasible.Through the analysis of the results of infrared spectrum,it can be preliminarily explained that the sugar chain in pumpkin polysaccharide is composed of furan sugar and pyranose,and there is a?-glycoside bond.2.Two kinds of sulfated pumpkin polysaccharide?SP-1 and SP-2?and phosphate pumpkin polysaccharide?PP-1 and PP-2?with different degree of substitution were prepared by chemical modification of pumpkin polysaccharide structure by HSO₃Cl-pyridine and POCl₃-pyridine methods.The degree of substitution of SP-1 and SP-2were 0.35 and 0.65,respectively.The degree of substitution of PP-1 and PP-2 were 0.01and 0.02,respectively.Then the sugar content,degree of substitution,infrared spectrum and nuclear magnetic resonance carbon spectrum of the four chemical modified products were determined.The results showed that sulfated pumpkin polysaccharide and phosphate pumpkin polysaccharide with different degree of substitution were successfully prepared.3.Pumpkin polysaccharide and its sulfated?SP-1,SP-2?and phosphorylated?PP-1,PP-2?derivatives with different degrees of substitution were studied by UV,three kinds of antioxidant tests?·OH scavenging ability,O₂^-·scavenging ability,reduction ability?were carried out in vitro,and V_C was used as a positive control.The experimental results showed that for sulfated products with different degrees of substitution,the scavenging effect of SP-1 and SP-2 on·OH was not significantly different in general.However,it could still be seen that the scavenging effect of SP-2 was better than that of SP-1,but both of them were lower than that of V_C and pumpkin polysaccharide.For the scavenging of O₂^-·,SP-1 and SP-2 had better scavenging effect than pumpkin polysaccharide.At lower concentrations,the scavenging capacity of SP-2 was similar to that of V_C,and it could be clearly seen that SP-2 had better scavenging ability than SP-1.For the reducing ability,the reduction ability of V_C was the best,while the reduction ability of SP-1 and SP-2 was lower than that of pumpkin polysaccharide.For phosphorylated products with different degrees of substitution,the scavenging capacity of PP-1 and PP-2 on·OH was stronger than that of pumpkin polysaccharide,however,both were lower than V_C,and the EC₅₀0 value of PP-2 is only 2.4 mg/mL.Moreover,it was obvious that the scavenging capacity of PP-2 was higher than that of PP-1.For the ability of PP-1 and PP-2 to remove O₂^-·,the scavenging ability of V_C was still the best,but the scavenging ability of PP-1 and PP-2 was obviously stronger than that of pumpkin polysaccharide.At a low concentration,the scavenging effect of PP-2 was better than that of PP-1.However,at high concentrations,the scavenging capacity of PP-1 was significantly higher than that of PP-2,and the EC₅₀0 value of PP-1 was only3.0mg/mL.For the reduction ability of PP-1 and PP-2,V_C still had the best reduction ability,but compared with pumpkin polysaccharide,although the overall difference was not significant,but still lower than the reduction ability of pumpkin polysaccharide.In general,pumpkin polysaccharide and its four different degrees of substitution of sulfated?SP-1,SP-2?and phosphorylated?PP-1,PP-2?products were successfully prepared.The experiment of antioxidant activity showed that after chemical modification with different degrees of substitution,it could enhance the antioxidant activity of pumpkin polysaccharide,which provided an experimental basis for further study of the antioxidant activity of pumpkin polysaccharide.