植物甾醇的亲水修饰、构效关系及分子机制研究

Cardiovascular disease and cerebrovascular disease has become the major causes of morbidity and mortality in human, and dyslipidemia is the leading risk factor for cardiovascular and cerebrovascular disease. Phytosterols are a class of natural active ingredients with hypolipidemic function. However, phytosterols are insoluble in water and poorly soluble in oil, which greatly restricts their practical application. So far, there have rare related report to improve their water solubility by molecular modification. The present study aims to improve their solubility in water without affecting their biological activity, starting from the molecular structure by molecular modification with polyethylene glycol as the hydrophilic modification agent in ionic liquid through “two steps” reaction. Water-soluble phytosterol derivatives will be synthesized and a efficient and green reaction system of water-soluble phytosterol derivatives will be established through the screening of ionic liquids and hydrophilic modification agent, combining with infrared spectrum, mass spectrum, nuclear magnetic resonance and chromatography analysis. On the basis of the synthesis of water-soluble phytosterol derivatives, their biological activity and the structure-activity relationship of phytosterols and phytosterol derivatives will be clarified by animal experiment using mice as animal model by dietary intervention. The regulation of phytosterol derivatives on the gene expression of protein, enzyme or receptor related to cholesterol metabolism by real time quantitative polymerase chain reaction technology, and the effect of phytosterol derivatives on the liver using chromatography and pathological section analysis will be studied to explore the possible molecular mechanism of cholesterol-lowering. This project will widen the application of phytosterols into food containing water and provide the scientific basis for their development and utilization.

心脑血管疾病已成为人类死亡的主要原因，而血脂异常是主要诱因。植物甾醇是一类具有降血脂的天然活性成分，然而它具有水不溶、油溶性低等特点，极大地限制了它的应用。目前国内外鲜有利用分子修饰方法改善植物甾醇水溶性的报道。本项目旨在不影响其活性前提下，从分子结构入手，以聚乙二醇等作为亲水修饰剂，在离子液体体系通过“两步”反应对植物甾醇进行修饰以改善其水溶性。通过离子液体、修饰剂的筛选，结合红外、质谱、核磁和色谱技术，建立水溶性植物甾醇衍生物的高效、绿色合成反应体系。在此基础上，以小鼠为动物模型，通过膳食干预研究修饰前后植物甾醇的结构与生理活性之间的变化，明确产物的构效关系。采用荧光定量PCR技术研究植物甾醇衍生物对胆固醇代谢相关蛋白、酶或受体基因表达的调控，结合色谱、病理切片等技术研究对肝脏影响，探讨可能的分子作用机制。本项目的实施，拓宽了植物甾醇在含水食品中的应用，为它的开发利用提供了科学依据。

植物甾醇是一类具有降脂功效的天然活性成分，然而其化学结构决定了它具有油溶性低、水不溶等特点，极大地限制了它的实际应用。通过分子修饰方法可以显著改善植物甾醇的油溶性，然而鲜有通过类似方法改善其水溶性的研究。本项目以不同分子量的聚乙二醇作为亲水修饰剂，分别通过化学-脂肪酶催化、路易斯酸催化、酸功能化离子液体催化等方法合成了一系列水溶性植物甾醇衍生物，其水溶性有了显著改善，可以达到7 g /100 mL。通过催化剂和修饰剂的筛选、合成路径的比较，结合红外光谱、质谱、核磁共振波谱和液相色谱，建立了“两步”、“一锅法”合成水溶性植物甾醇衍生物的高效、绿色合成反应体系。在此基础上，以高脂饮食诱导的SD大鼠为动物模型，考察了不同水溶性植物甾醇衍生物的降脂功效。结果表明，新合成的水溶性植物甾醇衍生物仍保留游离甾醇的降胆固醇功效，主要表现为降低血清TC水平、LDL-C水平，对TG和HDL-C水平无显著影响。通过实时定量PCR分析发现，水溶性植物甾醇衍生物通过影响肝脏中与胆固醇代谢相关蛋白、受体mRNA水平从而达到降低胆固醇的目的。通过本项目，植物甾醇的水溶性得到了显著改善，为植物甾醇的开发利用奠定了坚实的理论基础。