基于TDDFT方法及分子结构解析红曲色素的光降解机理

The weak photostability has seriously restricted the wide utilization of monascus pigments in food industries, and their photodissociation mechanisms are unclear yet. Time-dependent density functional theory (TDDFT) will be performed to optimize the geometries of ground states, excited-states of the main components of monascus pigments obtained by separation and extraction. Comparing the bond length, bond energy and electrons distribution between carbon atoms in the optimum geometric configuration, the photodissociation location and difficulty degree of monascus pigment molecule are analyzed, and the possible photodissociation mechanism of monascus pigment is deduced. The chemical structure of monascus pigment before and after photodissociation are compared by accurate chemical structure analysis methods, and the photodissociation mechanism of monascus pigment is described in molecular structure level. Some chemical groups are selected to prevent monascus pigment photodissociation by time-dependent density functional theory (TDDFT). Photostable monascus pigments derivatives containing the chemical groups will be produced by Monascus cultivated in fermentation medium with addition of compounds containing these chemical groups. The study will provide theoretical and technical basis for the elucidation of photodissociation mechanism of monascus pigments, and for the fermentation of photostable monascus pigments derivatives.

红曲色素见光易分解的缺点严重制约了其在食品工业中的应用，关于红曲色素的光降解机理却不清楚。本项目采用含时密度泛函方法（TDDFT）对分离获得的红曲色素主要组分的基态、激发态的最佳几何构型进行优化，根据最佳几何构型下碳原子之间的键长、键能、电子重排情况等，解析红曲色素各组分分子中发生光分解的部位及难易程度，推断红曲色素的光降解机理；通过精准的化学结构分析方法对红曲色素各组分光降解前后的化学结构进行测定、比较分析，从分子结构水平解析红曲色素的光降解机理；采用TDDFT方法从化学结构理论计算的角度分析筛选出能够阻止红曲色素光褪色的化学基团，将含有这些基团的化合物加入发酵培养基中，通过发酵过程中红曲霉的色素合成途径将底物中的这些化学基团转移到色素分子结构中，发酵生产出光稳定性高的红曲色素。本课题的完成将为红曲色素光降解机理的阐述及光稳定性高的红曲色素的发酵生产提供理论和技术依据。