人参皂苷的系统制备及其神经保护的构效关系研究

Ginsenosides are an important class of plant secondary metabolites, which showed very good pharmacological activities. Researchers found some ginsenosides exhibited remarkable neuroprotective activities. However, since the composition and structure of sugar moieties in ginsenosides varies, the relationship of structure - neuroprotective activity is still unclear. Therefore, preparation of ginsenosides library then studying the effects of number, composition and structure of the sugar moieties on their function would be helpful for deeply understanding the structure – activity relationship of glycoside compounds, as well as supplying theoretical basis for the application of ginsenosides. In this project, we will isolated and purified natural ginsenosides from ginseng; series of deglycosylated metabolites would be prepared using the ginsenoside - degrading enzymes to construct a relatively complete ginsenoside library with various sugar moieties amounts, compositions and structures; the neuroprotective activities of various ginsenosides would be systematically studied, the effects of number, composition and structure of the sugar moieties on the neuroprotective activity would be explored, and the structure – activity relationship would be concluded. The innovation of our project is that systemically explore the preparation of ginsenosides library, and the structure-activity relationship of ginsenosides in neural protection. The results would be helpful for deeply understanding the structure-activity relationship of plant natural products and reasonable utilization of precious medicinal plant resources.

人参皂苷是重要的植物次生代谢产物，药理活性显著且多样。研究表明某些人参皂苷具有良好的神经保护活性。但皂苷糖基组成不同、结构多样，目前对其神经保护活性的构效关系了解甚少。因此，制备完整的人参皂苷分子库，研究糖基数目、组成和结构对其功能的影响，既有助于深入理解糖苷化合物的构效关系，也能为其应用奠定基础。本项目拟从人参中分离纯化系列天然人参皂苷；利用微生物水解人参皂苷的糖苷键，生物转化制备系列人参皂苷衍生物；建立相对完整的天然人参皂苷及其衍生物的分子库。系统研究人参皂苷的神经保护活性，明确侧链糖基的数目、组成和结构对其神经保护活性的影响，归纳其神经保护活性的构效关系。本项目的特色和创新在于系统制备比较完整的人参皂苷分子库，全面探讨人参皂苷神经保护活性的构效关系。研究结果将为深入理解植物天然产物的构效关系提供丰富的信息，为糖苷类分子的应用奠定基础。

人参皂苷是重要的植物次生代谢产物，是具有应用潜力的候选药物分子。研究表明某些人参皂苷具有良好的神经保护活性。但皂苷糖基组成不同、结构多样，目前对其神经保护活性的构效关系了解甚少。基于此需求，本项目利用微生物分泌的糖苷水解酶及从微生物中克隆表达得到的重组糖苷水解酶水解人参皂苷的糖苷键，生物转化制备系列人参皂苷分子；系统研究人参皂苷的神经保护活性，明确人参皂苷的神经保护活性。本项目利用人参皂苷降解细菌—锰矿赖氨酸芽孢杆菌转化人参皂苷Rb1制备Rd；利用人参皂苷降解真菌—黑曲霉分泌的人参皂苷水解酶转化二醇型人参皂苷Rb1制备低糖基化皂苷分子F2、compound K；利用人参皂苷降解细菌——纤维化纤维菌的胞外皂苷水解酶转化二醇型皂苷Rb1制备Rg3、Rh2、compound Y、人参皂苷Mc、二醇型皂苷元PPD；转化三醇型皂苷Re制备Rg2。并进一步从纤维化纤维菌中克隆人参皂苷水解酶基因并在大肠杆菌中进行异源表达，利用表达的重组人参皂苷水解酶转化二醇型人参皂苷，制备一系列人参皂苷分子。对微生物中分泌的人参皂苷水解酶和重组表达的人参皂苷水解酶进行了系统的表征。对人参皂苷的神经保护活性进行了研究，发现人参皂苷Rg2能抑制H2O2诱导的脑皮质神经元细胞凋亡，并能通过增强phosphoinositide 3-kinase/Akt信号途径来对抗β-amyloid25-35诱导的凋亡，从而起到保护PC12神经细胞的作用。本课题的研究结果为人参皂苷分子的制备和分离提供了可行的路线，并为人参皂苷作为药用分子的应用奠定了基础。