离子液体/盐双水相气浮浮选体系对杜仲环烯醚萜选择性分离的机理研究

Both ionic liquids/salt aqueous two-phase systems and aqueous two-phase flotation technology have wide application prospect in the separation and purification of natural products. The iridoids from Eucommia ulmoides Oliver are a kind of important bioactive components to treat hepatic and inflammatory conditions. There are some problems of low selectivity and low efficiency using traditional methods to isolate these iridoids, so the new methods for separating iridoids from E. ulmoides need to be established in order to enhance separation efficiency. Nowadays, both ionic liquids/salt aqueous two-phase extraction and aqueous two-phase flotation have been studied and used for product recovery and purification. But a new combination method with ionic liquids/salt aqueous two-phase extraction and aqueous two-phase flotation has not been established, and its mechanism has not also been reported in the separation and purification of iridoids from E. ulmoides. In this study, in order to establish ionic liquids/salt aqueous two-phase systems, a series of task-specific ionic liquids would be designed and synthesised through adding special reactive groups of amino and hydroxyl on alkyl imidazole, and some free affinity ligands would be also added. Furthermore, a new combination method with ionic liquids/salt aqueous two-phase systems and aqueous two-phase flotation will be established to isolate selectively iridoids from E. ulmoides. And the relationships of structures of ionic liquids, flotation conditions, organization characteristics of E. ulmoides, and target iridoids would be investigated. Finally, the flotation effects of ionic liquids/salt aqueous two-phase systems, free affinity ligands and flotation conditions would be deeply investigated to determine the mechanism, and the separation behaviors and rules of target iridoids in ionic liquids/salt aqueous two-phase systems would be also revealed. The results not only will provide a new technology for the separation of iridoids from E. ulmoides, but also will provide a new path and theoretical basis for the separation of other natural products.

离子液体/盐双水相和双水相气浮溶剂浮选技术在天然产物的分离中具有广阔应用前景。杜仲环烯醚萜是一类具有保肝和消炎等功效的活性成分，传统的系统分离法存在选择性差和效率低等缺点，寻找更有效的分离技术可为提高分离效率提供新的途径。目前，离子液体/盐双水相和双水相气浮溶剂浮选技术已在天然产物的分离中开始应用，但两种技术联用及在杜仲环烯醚萜分离中的机制研究还未见报道。本项目将在咪唑类离子液体上引入氨基和羟基等亲和配基，或加入亲和配体，构建离子液体/盐双水相体系，并与双水相气浮溶剂浮选技术联用，重点研究杜仲环烯醚萜的分离选择性，分析离子液体结构、浮选条件及杜仲组织特点与环烯醚萜分离的关系，明确离子液体/盐双水相体系、自由亲和配体和浮选条件等因素对目标分子影响的机理，揭示杜仲环烯醚萜在该体系中的迁移行为与规律。研究成果不仅可为杜仲环烯醚萜的分离提供新的技术，还可为其他天然产物的分离提供新的路径与理论依据。

杜仲中富含京尼平苷酸(GPA)和桃叶珊瑚苷(AU)等环烯醚萜，该类成分极性相近，使用传统方法分离难度大。离子液体(ILs)作为一种绿色高效的萃取剂，因其结构、极性可设计，在相似极性物质的萃取分离中应用广泛，效果明显。本项目基于盐析效应、亲/疏水性效应和温度响应等构建了3类ILs基液-液萃取体系，利用单因素优化与计算机模拟等策略开展了内部因素(ILs类别、浓度)、外界因素(温度、时间、pH、体积流量等)对GPA和AU的萃取分离研究，建立了[C4mim]Br/K2CO3双水相体系、亲/疏水DESs双相体系和热响应P4444BzIm/水双相体系高效萃取分离GPA和AU的方法。发现了GPA和AU在[C4mim]Br/K2CO3双水相体系中富ILs相的富集效率达99.99%(EGPA)和96.95%(EAU)；结合N2浮选该体系对杜仲叶水提液中GPA的浮选效率和富集倍数达99.25%和125.83，远优于乙醇/NaH2PO4和正丁醇/水体系；通过阴离子交换将亲水ILs转变为疏水ILs，实现了回收。发现了相比和磷酸盐缓冲液对GPA和AU在四丁基氯化铵-己酸(疏水)/氯化胆碱-苹果酸(亲水)两相体系的分配影响较大，利用单因素优化体系的选择性系数达71.99，实现了杜仲雄花GPA和AU的选择性分离(上相EGPA = 94.59%，下相EAU = 80.41%)，效果优于正丁醇/水体系。发现了热响应[P4444]BzIm的温度依赖性与N和P原子密切相关，25%[P4444]BzIm/水体系对杜仲雄花中GPA的超声提取效率达0.23 mg/g，温控分相后富水相中GPA的回收率达91.95%，5次循环实验后，GPA和IL的回收率有一定下降。利用密度泛函理论和分子动力学模拟，揭示了分子间氢键的强弱是不同体系高效萃取分离GPA和AU的主要驱动力。所提出的ILs基液-液萃取分离方法，以生态的、温和的方式解决了杜仲中GPA和AU的有效分离问题，展现了在天然环烯醚萜萃取分离中的潜力，为其他新型绿色萃取体系的构建及天然产物的有效分离提供了借鉴。执行期内培养研究生3名，发表论文7篇，SCI 收录3篇，EI收录1篇，授权专利2项，在投论文1篇。