| The cyclodextrins(CDs) are cyclic oligosaccharides which have the special structure of “hydrophobic cavity coexisting with hydrophilic out-surface”. They can interact with a variety of organic compounds and form inclusion complexes selectively through hydrogen bonding, hydrophobic interactions and other secondary bond, according to the shape, size and polarity of the guest molecules. This property can be applied to the adsorption and separation of some natural products. The study of preparation, characterization and application of ?-cyclodextrin polymer will provide potential value for the applications of the natural products separation.In this work, ?-cyclodextrin-polyurethane(?-CD-PU) adsorbents which possess good thermal stability and mechanical properties have been prepared by crosslinking ?-CD with hexamethylene diisocyanate(HDI). Reactants ratio, crosslinking temperature and time and other conditions have been investigated and optimized during the process. The adsorbents obtained have the particle size of 0.4~0.8mm and pore diameter of 3.41 nm. The optimal technical parameters are: the HDI:?-CD mass ratio of 2:1; nanoscale MgO as the porogen; the pre-polymerization temperature of 50 oC; liquid paraffin and pump oil GS-1 mixed with mass ratio of 1: 3 as the oil phase; the mass ratio of oil to polymer solution at 4:1; the content of dispersant tween-80 at 0.25%(w/w) on the oil phase; stirring speed of 500~600 rpm. It is found that the technology shows good reproducibility.A new attempt to study the ?-CD-PU adsorption properties whith natural products in aqueous solutions is carried out by selecting the bio-active molecule corilagin and gallic acid as models, and the separation mechanism is discussed as well. The result shows that ?-CD can form 1:1 inclusion complex with corilagin, and the inclusion constant of them is 1.69×103 L/mol, revealing that the ?-CD domain is likely to provide an important contribution to the adsorption process. The isothermal adsorption equilibrium follows the dual-mode adsorption equation, and the adsorption mode belongs to microporous multilayer adsorption. While the dynamic adsorption efficiency is not as high as static adsorption efficiency.The practical application of ?-CD-PU is carried out for separating and enriching the effective component corilagin from Phyllanthus reticulatus. The ethanol crude extract is dried and then dissolved with water. The solution is directly loaded onto ?-CD-PU packed-column, and then successively washed with water and 20%(w/w) ethanol. The corilagin eluted from the column reached the purity of 64.8% and the purification factor of 5.4. The results demonstrate that ?-CD-PU adsorbent can achieve quick and efficient enrichment from P. reticulatus. It is expected that the novel adsorbent ?-CD-PU would be a promising candidate for active natural products separation and purification. |
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