【作者】 麻宁；

【导师】 袁直；

【作者基本信息】 南开大学 ， 高分子化学与物理， 2013， 博士

【摘要】 在天然产物化学中,天然产物的提取分离扮演着重要的角色,它不仅是天然产物及其衍生物化学发展的基础,同时它制约着天然产物的应用。而大孔吸附树脂以其高吸附容量,简单的工艺流程,吸引了许多研究者的关注。商品化大孔吸附树脂以苯乙烯等单体为骨架,其吸附作用以强疏水性为主,选择性较低,在工业应用上以天然产物的粗提取为主,无法进行更精细的分离提纯。为了使树脂能在更广泛的范围应用,必须对传统树脂进行改进,引入更多的吸附作用,同时在更大程度上优化其解吸条件。本论文从天然产物提取分离的需求出发,合成了以氢键吸附为主的几个系列吸附树脂,系统性的研究了以氢键作用为主的弱吸附作用应用于不同层次的天然产物分离纯化的过程。主要内容包括以下四个部分：第一部分：通过两种方法在疏水骨架的树脂上引入极性的酯基链段,通过对其红外的表征,验证了极性基团成功引入。然后,以汉防己生物碱为模型对两系列树脂及商品化树脂进行了静态吸附试验,其中DM和NDM系列树脂的吸附量均随极性单体的加入不断提高,但当其疏水骨架疏水性降低到一定程度时吸附量随之减小,这证明了疏水-偶极协同作用的存在,而NDM系列树脂因为极性链段相对集中大大增强了其偶极作用,所以其吸附量比DM系列树脂有明显增加。随后,在总碱的纯化过程中上述疏水-偶极协同作用再次得到验证,经NDM-20树脂纯化后,汉防己总生物碱的浓度达到93.2%。并通过精细调控pH和解吸附条件,根据汉防己甲素乙素PKa的差异设计了在不同pH下的分离试验,从而得到在pH=5.75时,其分离效果最好,因为这时处于分子态的汉防己甲素和离子态的乙素的比例最大,使得其在树脂上的保留能力出现明显的差别。最终得到汉防己甲素的纯度为93%以上。第二部分：在第一部分研究疏水-偶极协同作用的基础上,以疏水-协同作用为对照,研究了疏水-氢键的协同作用。合成了DE、DV两系列树脂,并以甜菊糖总苷的提取为实例,在静态吸附下计算了其等量吸附焓,发现疏水-氢键协同的DV系列树脂吸附焓明显高于疏水-偶极协同的DE系列树脂,证明在疏水作用相同时,疏水-氢键协同作用比疏水-偶极协同作用力强,增加其吸附作用。动态吸附中DV-20表现出了更高的吸附量更好的解吸附能力,与商品化树脂相比较,其吸附量增加了近一倍,而纯化后甜菊糖总苷纯度较商品化树脂有所提高。疏水-氢键协同树脂适合具有形成氢键能力的天然产物从动植物原料中大规模提取,由于疏水作用的存在,无法消除疏水作用广谱的吸附,所以不适合对单一组分的分离。第三部分：为了进行单一组分的分离我们需要摆脱疏水作用的限制,突出氢键吸附选择性吸附的优点,我们合成了以单一氢键吸附为主的树脂。为得到具有氢键吸附能力的聚乙烯醇链段我们选择了醋酸乙烯酯为聚合单体,选用与其结构相近的三烯丙基异氰脲酸酯(TAIC)为交联剂进行悬浮聚合,聚合完成后进行水解得到具有聚乙烯醇链段的VT系列树脂。通过红外表征发现醋酸乙烯酯树脂成功合成,并成功水解得到聚乙烯醇链段。以去除茶多酚提取物中的咖啡因为例,静态吸附表明：茶多酚上的酚羟基可与聚乙烯醇链段形成较强的氢键吸附作用,而咖啡因不能形成,与商品化树脂对照发现在咖啡因与树脂之间的吸附作用力为疏水吸附,而茶多酚既可以和树脂以疏水作用结合,也可以以氢键作用结合。因此,为了特异性的吸附茶多酚而去除咖啡因,应尽量降低树脂的疏水作用,同时增加其氢键作用。吸附热力学试验进一步说明VT树脂与茶多酚之间的氢键作用。我们利用动态吸附试验研究了VT-80树脂的动态吸附曲线,确定了其最佳上柱容量,并在此基础上做了梯度解吸。据此我们建立了基于VT-80树脂用来去除茶多酚提取物中的咖啡因的生产工艺。最后,我们检测了不同比例的茶多酚提取物中咖啡因的去除试验,并检测了树脂的再生性能和重复使用性能。最终产物中茶多酚的回收率大于92%,而其中咖啡因则被完全去除。第四部分：为了进行更为精细的分离,水体系下,由于水分子对氢键的干扰氢键作用不能完全发挥,对形成氢键能力相近的物质单一氢键吸附不能满足其分离的要求,因此需要在非水体系下进行多氢键协同吸附。为此我们选择了较为亲水的骨架,为了便于合成不同链长的功能基链,我们以丙烯酸酯系交联剂与甲基丙烯酸缩水甘油酯(GMA)聚合,通过调节交联剂的比例,选了合适的交联度,并在此基础上通过调控致孔剂的比例和用量,得到环氧含量最大的GT-3-4树脂作为树脂前体。首先以不同的功能基团对环氧开环,发现胺基作为受体能与羟基形成较强的氢键作用。通过不同长度柔性多胺链对树脂进行功能基化,得到GTN系列树脂,通过静态吸附试验发现在柔性链增长时树脂接枝链和甜菊糖总苷糖环间可形成多氢键协同吸附作用,形成氢键的个数与接枝链长和糖环个数有关。同时,研究了各种不同链长的低级醇溶剂对树脂氢键作用的影响,发现随着溶剂醇链长的增加,树脂与甜菊苷(SS苷)之间的氢键吸附焓绝对值越来越大,而在水溶液中其吸附焓为正值,说明水是树脂与SS苷之间氢键良好的破坏剂。在对甜菊糖总苷溶液动态分离实验中,选用了不同溶剂的上柱液研究溶剂对其分离性能有明显影响,通过不同比例的水作为氢键的破坏剂可特异解吸SS苷和RA苷(莱鲍迪苷A),但水对氢键的破坏过于强烈使得分离不容易控制,于是选用破坏能力稍弱的甲醇作为其破坏溶剂,进行解吸附,最终得到SS苷纯度为92.3%,RA苷纯度为91.4%,收率为73.2%。综合以上,疏水-偶极、疏水-氢键协同树脂适合对天然产物的大规模提取,但由于疏水作用的存在树脂对单体分离的难度较大,为了进行天然产物单体分离,我们设计了以氢键吸附作用为主的VT系列树脂,并用它成功的去除了茶多酚提取物中的咖啡因,但水溶液中由于水分子干扰势必影响氢键的发挥,同时对氢键形成能力相近但氢键个数不同物质的分离,单一氢键吸附很难发挥作用,为此我们在非水体系下,合成并研究了柔性多胺链的接枝树脂对甜菊糖总苷中SS苷与RA苷的分离,证明了多氢键协同吸附的存在,并在此体系下优化其分离工艺,最终得到较纯的RA苷。三种不同类型的树脂适用于不同层次的天然产物的分离提取。更多还原

【Abstract】 Extraction and separation of natural products play an important role in the chemistry of natural products. It is not only the basis for the research of natural products and their derivatives, but also restricts the application of natural products. Macroporous resin, which has high adsorption capacity and simple process, attracted the attention of many researchers. Commercial macroporous adsorption resins which were synthesized by monomers such as styrene, had a hydrophobic skeleton and its adsorption force was strong hydrophobic interaction. Their selectivity was low, which were mainly used in crude extracts of natural products in industrial applications. Commercial macroporous adsorption resins could not be used in a rigorous separation. In order to make resins applied in a wider range, traditional resin must be improved. More adsorption interactions should be introduced into adsorption resins, at the same time, optimizations should be researched on the analysis conditions. This thesis based on the natural product extraction and separation requirements, several series of hydrogen bonding adsorption resins were synthesized. Hydrogen bonding interaction of adsorption, which was applied to different levels of process of separation and purification of natural products, was studied systematically. The main contents include the following four parts:Part Ⅰ:Two methods were introduced in synthesis of the hydrophobic skeleton resin with the polarity of the ester group segments, the polar group segments was validated successful introduced into the resins by FT-IR characterization. Then, Tetrandrine alkaloids, as a model, were used to characterize two series of resins and commercial resins by static adsorption tests. Adsorption capacity of DM and NDM series resins rose as the addition of polar monomer improving, continuously. When the hydrophobicity of the hydrophobic skeleton was reduced to a certain extent, the adsorption capacity decreased suddenly, which proved the presence of a hydrophobic-dipole synergistic effect. NDM series resin had higher adsorption ratio than DM Series, because the high concentration polar segments of NDM series greatly enhanced its dipole interaction. The adsorption ratio of NDM resins has increased significantly. Subsequently, the hydrophobic-dipole synergy was verified again in the purification process of the alkaloids. After purification by NDM-20resin, the purification of tetrandrine alkaloids reached93.2%. Based on different PKA of the the TET and FAN, separation tests were designed at different pH and desorption conditions. The separation had a best result in pH=5.75, because TET was in molecular state and FAN was in ionic state in this pH, making its retention different on the resin, significantly. TET purity of product was more than93%, finally.Part II:based on the study of the hydrophobic-dipole synergy in the first part, the hydrophobic-hydrogen synergistic effect was researched as the hydrophobic-dipole synergy, in this part. DE and DV Series resins were synthesized and Extraction of stevia glycosides was used as a model. The static adsorption was used to calculate the adsorption enthalpy, which showed the hydrophobic-hydrogen synergy existed in DV series resin. The adsorption enthalpy of hydrophobic-hydrogen synergy was significantly higher than the hydrophobic-dipole synergy in DE series resins, to prove that in the same of the hydrophobic interaction, hydrophobic-hydrogen bonds synergy was stronger than the hydrophobic-dipole synergy, which increased the adsorption of DV resins. Dynamic adsorption on the DV-20showed higher adsorption and better desorption compared with the commercial resins. The adsorption amount was nearly doubled, and the purity of stevioside was higher than the purity of commercial resins. The hydrophobic-hydrogen synergistic resins were suitable for large-scale extraction of natural products from plant or animal raw. Impurity, which could form hydrogen bonds, could not be eliminated due to the presence of a hydrophobic interaction, hydrophobic interaction broad spectrum of adsorption. It was not suitable for the separation of a single component.Part III:In order to obtain single component, we need to get rid of the limitations of the hydrophobic effect and project advantage of hydrogen adsorption which had high selectivity in adsorption. A series of resins were synthesized based on single were polymerizable monomers for suspension polymerization. Hydrolysis carried out after the completion of polymerization, to give the VT series resin. The synthesis of vinyl acetate resin and s hydrolyzed to obtain the polyvinyl segments were successful, which was showed in FT-IR characterization. Take removing the caffeine from the tea polyphenol extract for example. The static adsorption showed:there was a strong hydrogen adsorption interactive between a phenolic hydroxyl group on tea polyphenols and polyvinyl alcohol segments, while the caffeine cannot form. The adsorption of commercial resins showed there was hydrophobic adsorption between the caffeine and the resin, while the tea polyphenols also could form it. Accordingly, for the specific adsorption of tea polyphenols removed and the resin, the hydrophobic effect of the resin should be minimized, while hydrogen bonding interactions should be increased the adsorption thermodynamics tests further illustrated the role of hydrogen bonds between the VT resin and polyphenols. Dynamic adsorption curve of VT-80resin was plotted to determine the best capacity of the dynamic adsorption, and the gradient desorption carried out, based on this. Accordingly, we established the production process of VT-80resin used to remove the caffeine in the tea polyphenols extract. Finally, we examined the different proportions of caffeine in tea polyphenols extracts removal tests, and detected regeneration of resin and re-use performance. The recovery of the final product polyphenols was more than92%and caffeine was completely removed.Part Ⅳ:For rigorous separation, due to the interference hydrogen bonding of water molecules, hydrogen adsorption cannot take full advantage of adsorption in water system. The single hydrogen bonds adsorption cannot meet the requirements of the separation of similar substances forming similar hydrogen bonds. Multi-hydrogen bonds adsorption was required in the non-water system. To this purpose, more hydrophilic skeleton were chosen. Polymerizable acrylate ester-based cross-linker agent and GMA were chosen as monomers, in order to facilitate the synthesis of different chain length of functional groups. Then the proportion of cross-linker agent and the pore-foaming agent were adjusted, to select the appropriate degree of crosslink. GT-3-4resin was chosen as the resin precursor for the most amount of epoxy group. First, different functional groups were used in epoxy opening reaction, and the static adsorption showed that amino group was the best hydrogen acceptor and could form strong hydrogen bonding interaction with the hydroxyl. GTN series resins were synthesized through different length of the flexible function agents. Static adsorption tests showed as the flexible chain growth in grafted resins, stevia glycosides could form more hydrogen bonds with the GTN resins. The number of hydrogen bonds formed between resins and adsorbate, was related with the grafted chain length and the number of sugar ring. A variety of different length of the alcohol solvents were studied, and found that with the increase length of solvent, absolute value of hydrogen bonding adsorption enthalpy between resin and SS glycosides was larger. The adsorption enthalpy in the aqueous solution was positive, which showed that water was destructive agent to hydrogen bond between resin and SS glycosides. In dynamic separation tests, the choice of the type of glycosides solutions had obvious influence on its separation performance. Different proportions of water could be used as the destruction agent of the hydrogen bonds, then SS and RA were specific desorption. But water as the destruction agent of the hydrogen bonds was too strong to control. So a weaker destruction agent methanol was selected as destruction solvent. In this desorption, we could obtain the product. The purity of SS was92.3%and the purity of RA was91.4%, yield was73.2%.Based on the analyze above, the hydrophobic-dipole synergy, hydrophobic-hydrogen synergy resins were suitable for large-scale extraction of natural products, but it’s difficult for rigorous separation, due to the presence of the hydrophobic interaction in resins. To rigorous separated natural products, we have designed a single hydrogen adsorption resins, VT series resins, and it was successfully used to remove the caffeine from tea polyphenols extracts. but due to the interference of water molecules in the aqueous solution, hydrogen bonds couldn’t be expressed. Sometimes, adsorbates had similar abilities in the formation of hydrogen bonds but different number. It’s hard to separate by single hydrogen bond adsorption resins. In non-aqueous system, we synthesized and studied flexible polyamine chains grafted resin on the separation of the SS and RA, demonstrated the presence of multiple hydrogen adsorption, and optimized the separation process of this system. Four different types of resins are suitable for the separation and extraction of natural products at different levels.更多还原