Preparation And Antioxidant Activity Of Rice Bran Polysaccharide And Its Derivatives

Rice bran,also known as rice husk,is the main by-product of rice processing.It is made from rice's exocarp and mesocarp and other structures.It is a rich and underutilized resource.Although the output of rice bran in our country ranks first in the world,our country ignores the rational use of rice bran and makes it only used as feed for livestock,which makes the use value of rice bran low.Rice bran has high requirements for the storage environment,and storage of rice bran will cost a higher cost.It is necessary to store the rice bran in a dry and cool place,otherwise it will quickly deteriorate.The reason is that rice bran is rich in lipase and has strong enzyme activity,so this limits the further development of the potential value of rice bran in my country.Rice bran polysaccharide(RBP)is one of the main active ingredients in rice bran.It is a heteropolysaccharide with a complex structure and a large molecular weight.The antioxidant activity of rice bran polysaccharide and their three derivatives are studied by identifying their reducing ability,anti-lipid peroxidation ability,DPPH scavenging ability,hydroxyl radical ion scavenging ability,and superoxide anion scavenging ability.In this experiment,the method of hot water extraction was used to extract the crude polysaccharides of rice bran polysaccharide from defatted rice bran.Through derivatization,carboxymethylated rice bran polysaccharide(CM-RBP),phosphorylated rice bran polysaccharide(P-RBP),and acetyl Rice bran polysaccharide(Ac-RBP).The rice bran polysaccharide and three derivatives were characterized by infrared spectroscopy,nuclear magnetic and ultraviolet characterization methods.The antioxidant activity of rice bran polysaccharide and their three derivatives are studied by identifying their reducing ability,anti-lipid peroxidation ability,DPPH scavenging ability,hydroxyl radical ion scavenging ability,and superoxide anion scavenging ability.1.The response surface analysis method was used to determine the optimal reaction conditions of the hot water extraction method.The reaction temperature was 100?,the reaction time was 5h,the solid-liquid ratio was 1:10;the volume ratio of polysaccharide and Sevag reagent was 2:1 when removing protein,and the volume ratio of n-butanol and chloroform in Sevag reagent is 1:4.The protein process was repeated 3 times;the rice bran polysaccharide was insoluble in alcohols,so ethanol was used to separate the rice bran polysaccharide.After experiments,it was found that when the ratio of ethanol volume to rice bran polysaccharide solution volume was 3:1,the amount of rice bran polysaccharide precipitated out was the largest.Using the method and conditions of this experiment,the polysaccharide yield of rice bran polysaccharide was 2.78%.2.In the experiment,the rice bran polysaccharide was modified by carboxymethylation,phosphorylation,and acetylation,and three derivatives of CM-RBP,P-RBP,and Ac-RBP were prepared respectively.The solubility of modified RBP was found there was a significant increase,while the molecular weight and viscosity were reduced.In the experiment,the polysaccharide content of RBP was 84.5%measured by the phenol-sulfuric acid method,the polysaccharide content of P-RBP was 68.8%,the polysaccharide content of CM-RBP was 60.2%,and the polysaccharide content of Ac-RBP was 63.7%;and acid-base was used.The degree of substitution of the carboxymethyl group and the acetyl group were determined to be 0.91 and 0.32respectively by the titration method,and the degree of substitution of the phosphate group measured by the ammonium phosphomolybdate method was 0.28.We had performed a series of characterizations on RBP and three derivatives.It has been found that?-D-glucopyranose was the main component of RBP,and through NMR spectroscopy,we found that RBP has?-1,4 and?-1,6 the two glycosidic bond forms,and the content of?-1,4 structure was relatively large.The UV spectrum was used to detect the protein content of rice bran polysaccharide and derivatives,and it was found that the protein content of rice bran polysaccharide after 3 times of deproteinization was extremely low,which showed that the Sevag reagent according to the ratio in this experiment could effectively remove rice bran polysaccharide free protein.3.Research findings on the in vitro antioxidant activity of chemically modified RBP.(1)Not all chemically modified polysaccharide derivatives had better activities than unmodified rice bran polysaccharide,such as the removal of acetylated rice bran polysaccharide.The activity of hydroxyl radical ions was not as good as rice bran polysaccharide itself,but after the other two modifications,the derivatization activity of rice bran polysaccharide was indeed better,and the antioxidant capacity will increase with the increase of concentration;(2)The antioxidant activity of P-RBP is the best among several derivatives,and it has greatly improved various antioxidant activities of rice bran polysaccharide,especially in the anti-lipid peroxidation activity test with high concentration(3.2g/L)phosphorylated rice bran polysaccharide(P-RBP))Even exceeded the activity of the control group V_C.In other activity tests,the activity of V_Cas a control group was much higher than that of rice bran polysaccharide and its derivatives,so this was worth paying attention to.And under the DDPH scavenging ability test,it was also found that the activity of phosphorylated rice bran polysaccharide was much higher than the activity of rice bran polysaccharide and the other two derivatives;(3)It was found that the activity of acetylated rice bran polysaccharide was the best under the superoxide anion scavenging test.,The activity of several other products was basically the same at high concentration(3.2g/L).In short,this topic has studied the preparation of rice bran polysaccharide and itsderivatives and in vitro antioxidant activity,and used various methods for characterization,which will provide some data support for a more in-depth understanding of the biological activity of the polysaccharide derivatives in the future.