水难溶性树木源活性成分的溶出新策略：离子液体-分子溶剂-酶复合体系

The extraction techniques based on ionic liquid as solvent have been used in the separation of plant active ingredients. Although ionic liquids have been used as attractive green alternatives to conventional volatile organic solvents in various applications, high viscosity of ionic liquid brings about its worse permeability for plant matrix. Many researches resolve permeability problem by using microwave or ultrasonic assisted extraction method, but these physical methods have some disadvantages, such as high-investment, small scale, high energy consumption and high radiation. Because of using water as a co-solvent, the current studies have limit to the separation of the high polarity and moderate polarity components. The cell wall of woody plant is highly fibrotic and lignified, its multi-scale complicated structure bring out the mass transfer barrier effect which makes it difficult for the solvent to penetrate into the interior of the plant cell. So as to improve these problems, we come up with an idea to set up ionic liquids-high boiling point molecular solvent-enzyme (IL-HPMS-CH) composite system. Dihydroquercetin, camptothecin etc.are chosed as target water insoluble compounds. In the proposed method, we will study physicochemical properties of ionic liquid-molecular liquid binary solvents, select a series of extraction solvent system applicable for trees and make clear its role on the target component extraction action as well as the selectivity rule. The dynamic mass transfer process under the action of hydrolase (cellulase, pectinase, xylanase) will be investigated. And the mechanism of the enhanced extraction by IL-HPMS-CH will be discussed by observing material characterization results of trees matrix. Raman hyperspectral imaging system was used to analysis the content and distribution of tree cell wall components. This research provides new view and method in the application of ionic liquid in the complex system of trees for separation and analysis of water insoluble component. And the research will provide a theoretical basis for finding efficient, green and feasible solvents and method for the separation of active ingredients from high-fiberized trees.

绿色溶剂离子液体已应用在植物活性成分的分离工作中，虽然离子液体有优于传统溶剂的性质，但其粘度大、传质效率低，通常需其他物理方式促进传质过程；由于以水作共溶剂，目前的研究局限于极性、中极性成分的分离；而树木植物细胞壁高度纤维化、木质化，其多尺度结构带来的传质屏障效应，导致溶剂难以渗入到植物细胞内部。为解决以上问题，本研究选择水难溶性喜树碱、二氢槲皮素等为目标化合物，采用离子液体-分子溶剂-酶体系对其进行分离，探索目标化合物溶出与二元溶剂特性的量化关系，探索其在细胞壁水解酶作用下的动态传质过程，考察热力学、动力学因素，结合材料学表征技术分析树木基质在溶剂、酶作用后形貌、化学成分的变化，在拉曼高光谱成像系统中分析树木细胞壁成分的含量与分布，阐明离子液体-分子溶剂-酶体系下对难溶性成分实现分离的机理，为树木中活性成分的分离寻找高效、绿色、可行的技术提供理论基础。

在树木天然产物的制备中，由于植物细胞壁高度纤维化、木质化，其多尺度结构和复杂组分构效所带来的传质屏障效应，导致溶剂难以渗入到植物细胞内部，细胞内次生代谢产物溶出的不彻底，为树木源生物活性物质的制备带来不小困扰。我们设计的IL-HPMS针对上述问题创新地解决了传质屏障问题，即在IL-HPMS体系下，树木植物基质在超声辅助强化得作用下溶解充分，彻底打破固液传质屏障，做到活性小分子物质的全提取。借助离子液体溶剂体系[C4mim][OOCCH3]/DMSO对黄檗的生物碱类化合物进行分离。通过单因素优化、PBD和BBD模型对相关影响因素进行优化并确定分离生物碱类化合物的最佳条件。其中的影响因素包括离子液体摩尔浓度，液固比，超声温度，超声时间，超声功率和植物基质粒径，最佳条件下得到黄檗生物碱分离的平均得率为4.22 ± 0.20 mg/g。通过方法比较，充分证明了离子液体溶剂体系用于活性小分子成分分离的高效性和安全性。通过Kamlet-Taft溶剂化参数结果得出离子液体溶剂体系主要通过阴离子与纤维素分子之间形成新的氢键以断裂原植物材料中纤维素分子内和分子间氢键实现纤维素分子链的解离，阳离子与半纤维素分子乙酰基和木质素分子链之间的醚键等反应实现了植物组分在离子液体溶剂体系中的溶解。XRD结果显示植物材料在该溶剂体系中溶解再生分离会导致植物组分纤维素的结晶程度发生下降。扫描电镜结果表明处理后的植物原料物理结构的改变，增强溶剂渗入细胞组织从而加快细胞内活性物质的释放。以上结果从不同层面创新、探究活性成分的溶出过程，深入阐述了中药复杂基质中小分子活性物质萃取过程。离子液体—非质子溶剂联用技术突破中药植物活性物质全溶解的瓶颈，在此基础上实现生物活性小分子的高效分级和纯化，使林木活性成分得到高效、安全和彻底的分离，将为树木植物活性成分的制备提供一种新方法及理论，具有广阔的应用前景。我国在树木化学成分分析方面的研究还比较薄弱，通过对低粘度离子液体-非质子溶剂条件下复杂的植物化学组分的溶解、分离、分析研究，可以促进我国中药化学及树木化学成分分析领域中研究和技术水平的提高。