天然活性多糖的光催化降解机制及其构效关系研究

Polysaccharides from natural resources have relatively low biological activities which were restricted by their high molecular weights. They even cannot be absorbed by organism. Degradation is an effective method to improve the activities of these polysaccharides. This project will select some polysaccharids extracted from several Pharmaceatical and Edible natural resources, such as pleurotus tuber – regium(Fr.)Sing, lonicera japonica and Ampelopsis grossedentata as the research objects. We aimed at developing a method which could moderately and controllably degrade high molecular weight polysaccharides into low molecular weight ones. The photocatalytic reaction system which based on nano-titanium dioxide as medium has the advantages such as controllable and moderate reaction procedure, harmless to the environment, etc. However, it is seldom used in the area of polysaccharides degradation. Here, we intend to use this photocatalytic reaction system to achieve the aim of controllable, moderate degradation of polysaccharides. Then the structure-activity relationship will be elucidated. The first is to optimize the main factors which affecting the efficiency of photocatalytic degradation and also to study the degradation mechanisms. A universal polysaccharide degradation technique will hence be developed. Degradation fragments are then studied through detailed structure identification, molecular modification, in vitro and in vivo antioxidant activity and hypoglycemic activity screening experiments, etc. The structure-activity relationship of these polysaccharides will be revealed gradually and deeply. All these data will provide a theoretical basis for further studying the pharmacological activity of polysaccharides.

天然来源的多糖常因其过高的分子量造成其生物活性偏低，甚至无法被生物体吸收利用，而通过降解技术提高多糖活性是一种行之有效的方法。本项目选取几种地区特色天然药/食两用资源（虎奶菇、藤茶、金银花等）中的水溶性活性多糖作为研究对象，旨在探索降解技术对活性多糖的活性和结构即构效关系的影响。本项目拟将光催化降解技术应用于活性多糖的降解上，利用该体系环境友好和反应过程温和可控的优点，通过参数优化和控制得到降解程度可控的多糖片段，并结合不同类型多糖的结构特点研究其降解机制，据此可发展一种普适性的、可控、温和且无环境污染的光催化多糖降解技术。随后对得到的多糖降解片段进行详细的结构鉴定，并对各类型多糖的抗氧化活性、免疫活性、降血糖活性等功能进行优化筛选，逐步深入的揭示所研究多糖的构效关系，从而为提高天然多糖的活性及其应用开发研究奠定理论基础。

天然多糖的活性大小和多种因素相关，除了分子构成、构型构象等基本因素外，分子量是影响多糖活性的重要因素。本项目旨在探索一种新颖的降解技术——基于二氧化钛纳米粒子的光催化反应体系用于研究几种不同类型天然活性多糖的可控性适度降解，通过多方位考察多糖降解片段的结构信息和生物活性，分析其构效关系，为天然来源多糖的活性提高、药理研究和开发应用提供理论基础。.重点研究了虎奶菇、金银花、藤茶等几种原料中粗多糖的提取、纯化和性能表征等，研究了高效提取虎奶菇等原料中多糖的提取工艺，鉴定其单糖组成、分子量等基本结构信息和理化性质，为光催化降解实验提供不同纯度的样品。.多糖的催化降解技术研究，通过设计五因素三水平的正交实验来考察最佳实验条件。评价指标为多糖的分子量变化，通过凝胶渗透色谱（GPC）测定。除重点考察特选的几种活性多糖外，另外选取葡聚糖及市售常见多糖作为参照，全面考察光催化体系对不同类型多糖降解能力的普适性，并具体结合多糖的分子组成和结构特点分析其降解位点、降解程度等反应机制问题。并研究多糖的链构象表征二级结构信息，如分子量、尺寸、构象等。.通过光催化降解多糖体系的优化和应用，可方便的获得不同降解程度的多糖片段，继而利用这些多糖片段进行多糖的生化活性研究，具体包括体外抗氧化活性，降血糖活性等；并推导其构效关系，从而为天然活性多糖的开发应用提供技术支持和理论基础。