Research In Microwave-assisted Synthesis And Antioxidant And Hypolipidemic Effects Of Xylo-oligosaccharides

Xylo-oligosaccharide, as a new type of food additive, with its distinctive characteristics and better function than other oligosaccharides, is receiving greater attention. Oligosaccharide is usually synthesized by enzymes, which takes a long time and has low yield. Microwave-assisted synthesis of oligosaccharides in solid state has a rapid speed and high yield, it also has no environment pollution. In this thesis, oligosaccharides were synthesized assisted with microwave in solid state, xylose as the reactant, acid A as the catalyst. Proper methods of synthesis technology conditions assisted with microwave were studied. The free radicals scavenging effect of the synthetic oligosaccharides were studied, and we also investigated the antioxidant activites and hypolipidemic effects of the synthetic oligosaccharides in hyperlipemia rats.The optimum reaction conditions were investigated by single factor experiment and orthogonal test and the optimum reaction conditions are: microwave power 1000 w, microwave irradiation time 3.5 min, adding 17 % initiator, adding 9 % acid A as the catalyst. The yield of product was 84.86 %. The product was characterized by HPLC analysis. The constituter of product was established as follows: disaccharides 13.45 % %, trisaccharides 7.42 % %, tetrsaccharides and other polysaccharides 63.99 %.The hydroxyl radicals (·OH ) and DPPH radicals scavenging effects of xylo- oligosaccharides in different degrees of polymerizations(DPs)synthesized assisted with microwave in solid state were studied. The results showed that xylo-oligosaccharides had satisfactory scavenging activities to·OH , among the three xylo-oligosaccharides in DPs(LL,ML,HL), the xylo-oligosaccharides of high polymerization degree(HL)has most remarkable scavenging effects on·OH , IC50 was about 14 mg·mL-1. And the xylo-oligosaccharides had hardly scavenging effects on DPPH radicals.In order to investigate the antioxidant activities and hypolipidemic effects of xylo-oligosaccharides, the hyperlipidemic rat model induced from high-fat feed was used as experimental material. Different concentration of xylo-oligosaccharides were added in high-fat feed, then changes of free radicals(FR),SOD ,GSH-Px ,CAT ,T-AOC ,MDA and hypolipidemic effect were observed. The results showed that high–fat diet could result in rats oxidative stress and reduce antioxidation capability of rat significantly, and the levels of TC , TG and LDL-C were increased and HDL-C were decreased as compared to normal energy diets. Addition of xylo-oligosaccharides in the high–fat diets could enhance the activities of SOD, GSH-Px, CAT, increase the the level of T-AOC, decrease the FR and the content of MDA in serum and tissue effectively. It also decreased the levels of TC , TG , LDL-C and AI , increased the level of HDL-C siginificantly. The results indicated that xylo-oligosaccharides had antioxidant and hypolipidemic effects.