| 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. |
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