多酚-壳聚糖复合物的形成及其对多酚水溶性影响机制的核磁共振研究

Polyphenols are natural products with a variety of physiological activity, however, due to the hydrophobic aromatic groups in its molecular structure, a considerable number of polyphenols have poor water-solubility, resulting in decreased bioavailability which greatly limits its application in functional food. Natural active chitosan, as an ideal material capable of combining with polyphenols, provide a new approach to solve this problem. In this study, highly hydrophilic chitosan with low molecular weight is selected to interact with polyphenols under certain conditions to prepare a stable, water-soluble polyphenol-chitosan complex. NMR techniques, together with quantum mechanical calculation methods are used to study the molecular structure and three-dimensional conformation of the polyphenol-chitosan complex in water. Thus, the mechanism of effect of chitosan on water-solubility of polyphenols can be clarified based on the conditions of molecular interaction, the binding site and type of polyphenol-chitosan complex. Besides, the model of relationship between the molecular structure of polyphenol-chitosan complex and the water-solubility of polyphenols can be established. This study applies the interaction between functional food ingredients i.e. polyphenols and chitosan to improve the water-solubility of polyphenols, which provides theoretical foundation for improving the stability and bioavailability of functional food ingredients.

多酚类化合物是一类具有多种生理活性的天然产物，然而多酚分子结构中的疏水芳香基团使得相当一部分多酚水溶性极差，导致其生物利用度下降，极大限制了多酚在功能性食品中的应用。天然活性壳聚糖作为能够与食品功能组分相结合的理想材料，可与多酚进行相互作用，为改善多酚水溶性提供了新的思路。本项目选取低分子量、高亲水性的低聚壳聚糖，使其在特定条件下与低水溶性多酚相互作用，制备成稳定的、水溶性的多酚-壳聚糖复合物。拟采用核磁共振技术、辅以量子力学计算方法，研究多酚-壳聚糖复合物的分子结构和在水中的三维活性构象，从多酚与壳聚糖分子间相互作用的条件、作用位点及方式等方面阐明壳聚糖对多酚水溶性影响的机制，构建多酚-壳聚糖复合物分子结构与多酚水溶性之间的构效关系模型。本课题利用食品功能组分多酚与壳聚糖之间的相互作用来提高多酚水溶性，将为改善食品功能性成分的稳定性和生物利用度提供科学理论依据。

为了改善多酚的物理性质和生物活性，本项目采用了低分子量、高亲水性的壳寡糖，使其在喷雾干燥或冷冻干燥的条件下分别与低水溶性橙皮苷、柚皮苷、芦丁相互作用，制备成稳定的、水溶性的多酚-壳寡糖复合物，并评价了该复合物的苦味、抗氧化活性和抑菌性。采用了傅立叶远红外光谱法和核磁共振等技术研究了多酚-壳寡糖复合物的分子结构，结果表明，多酚芳香环上的氢原子易于通过氢键与壳寡糖上的氢原子结合，多酚的芳香环易于以疏水相互作用或范德华力等非共价键与壳寡糖结合，从而维持复合物的稳定构象。从每种多酚与壳寡糖分子间相互作用的条件、作用位点及方式等方面阐明了壳寡糖对不同多酚性质影响的机制，构建了多酚-壳寡糖复合物分子结构与多酚性质之间的构效关系模型。本课题利用食品功能组分多酚与壳寡糖之间的相互作用提高了多酚水溶性，降低了多酚苦味，且提高了其生物活性，为改善食品功能性成分的稳定性和扩展其应用范围提供了科学理论依据。