【作者】 丁苏；

【导师】 乐国伟；

【作者基本信息】 江南大学 ， 营养与食品卫生学， 2008， 硕士

【摘要】 低聚木糖,作为新型的食品添加剂,由于具有比其他低聚糖更优越的特性及功能性而越来越被人们所关注。低聚糖的合成通常采用酶法技术,合成时间长,纯度低而且存在废液污染。微波固相合成低聚糖以单糖或双糖为反应物,其反应速度快,合成率高且清洁无污染。本研究以木糖为反应物,在微波加热条件下固相合成寡糖混合物,探索了合适的反应条件,确立了合成工艺路线,对合成产物体外清除自由基活性进行了探讨,并研究了产物对高脂血症小鼠的抗氧化及降血脂功能。经单因素和正交实验得出以木糖为底物,以酸A为催化剂,利用微波固相合成寡糖最适反应条件为:微波功率1000 w,微波处理时间3.5 min,引发剂的添加量17 %,催化剂的添加量为9 %,合成率为84.86 %。HPLC分析:产物中二糖占13.45 %,三糖占7.42 %,四糖及以上占63.99 %。对微波加热固相合成的不同聚合度的低聚木糖﹛低聚合度(LL)、中聚合度(ML)、高聚合度(HL)﹜清除羟自由基(·OH)及DPPH自由基活性进行了研究。实验结果表明,低聚木糖对·OH具有较好的清除活性,高聚合度的低聚木糖对·OH的清除作用最显著,IC50为14 mg·mL-1。低聚木糖对DPPH自由基几乎没有清除能力。为了解低聚木糖的抗氧化与降血脂作用,以小鼠为研究对象,用高脂饲料诱导高脂血症模型,同时在高脂饲料中添加不同百分比的低聚木糖,观察不同实验组小鼠的血浆和组织自由基水平、SOD、GSH-Px及CAT活性、T-AOC、MDA含量以及血脂水平。结果表明:与正常对照组相比,饲喂高脂日粮可导致小鼠氧化应激,降低机体抗氧化能力,提高小鼠血浆TC,TG,LDL-C的水平,降低HDL-C水平。高脂日粮中添加低聚木糖能显著降低高脂血症小鼠体内自由基水平,显著增强血浆及组织中SOD、GSH-Px及CAT活性,增加T-AOC,显著降低MDA含量。低聚木糖还能显著降低小鼠血浆总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白-胆固醇(LDL-C)和动脉粥样硬化指数(AI),显著升高高密度脂蛋白-胆固醇(HDL-C)。因此,低聚木糖具有抗氧化和降血脂作用。更多还原

【Abstract】 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.更多还原