食源性多糖调控氧化应激作用机制是当前食品科学基础研究的热点之一。前期研究表明仙人掌果多糖具有显著的抗氧化应激活性，但相关机制尚不明确。鉴于此，本项目拟在前期研究基础上，从仙人掌果中分离出三种不同分子量的多糖组分，分析其理化性质和溶液构象特征，并表征其结构。在此基础上，利用四氧嘧啶建立氧化应激动物模型，给动物灌胃不同剂量和分子量的多糖组分，通过检测抗氧化酶和相关蛋白水平以及氧化应激敏感的信号通路分子蛋白水平，研究不同分子量的多糖组分对氧化应激的作用及构效关系，并从中筛选出一种活性强的多糖组分，利用过氧化氢诱导建立的胰岛β细胞氧化应激模型，进一步从蛋白和基因水平上探讨多糖对氧化应激的调控作用机制，并揭示Keap1-Nrf2/ARE信号通路是否参与氧化应激调控。通过本项目研究，旨在从分子水平上阐明仙人掌果多糖调控胰岛β细胞氧化应激作用的结构基础及机理，同时为食用仙人掌果新资源的开发提供理论依据。

It is becoming a hot topic to regulate oxidative stress by polysaccharides from foods in current research field of food science. Our previous studies have showed that polysaccharides from the fruits of Opuntia dillenii (Ker.-Gawl.) Haw. (ODFPs) exhibit significant anti-oxidative effect. However, the mechanism of action is not yet clear. In this project, based on our previous studies, three polysaccharide fractions with different molecular weights will be isolated from the fruits of O. dillenii Haw., and their physicochemical properties, conformational characterizations in solution will be investigated and chemical structures will be characterized. Using alloxan-induced oxidative stress model of mice, the mice will be intragastrically administered three polysaccharide fractions with different molecular weights at different doses, respectively, and the levels of some antioxidant enzymes and anti-oxidative proteins and oxidative stress-sensitive signaling molecules in serum, liver and pancreas of the mice will be determined, we will investigate the effects of polysaccharide fractions with different molecular weights on the mice against oxidative stress induced by alloxan and explore the relationship between the structures of polysaccharide fractions and anti-oxidative activity in order to find a polysaccharide fraction with strong anti-oxidative activity. We will further explore the molecular mechanisms underlying the effects of ODFPs on pancreatic beta cells against oxidative stress induced by hydrogen peroxide from the viewpoint of protein and gene. In addition, we will demonstrate whether the ODFPs protect pancreatic beta cells against oxidative stress damage via activating Keap1-Nrf2/ARE pathway. This project will elucidate physicochemical properties, conformational characterization in solution and chemical structures of ODFPs and the effects on pancreatic beta cells against oxidative stress and the molecular mechanisms. And it can also provide scientific evidences for the development of the fruits of O. dillenii Haw. as a new food.