Synthesis Of β-cyclodextrin Magnetic Composite Microsphere And Its Application On The Separation Of Corilagin

Magnetic polymer microspheres(MPs) show many advantages including magnetic responsiveness, easy for surface functionalization and excellent biocompatibility, which have been paid a wide range of attentions. 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. When the MPs modified with CD, it is possible to obtain the cyclodextrin/magnetic composite microsphere simultaneously possessing the unique properties of MPs(magnetism) and CDs(high supramolecular recognition and host-guest inclusion capability) through combining their individual characteristics. This property can be applied to the adsorption and separation of some natural products.In this work, the cyclodextrin magnetic composite microsphere(β-CDPU/MP) is fabricated by the Fe3O4 particles entrapped with β-CDPU. The magnetic particles are synthesized by coprecipitation method, then β-CDPU have been pre-polymerized by crosslinking β-CD with hexamethylene diisocyanate(HDI). Finally β-CDPU grafted onto the surface of magnetic particles. And the composite microsphere was charactererized by XRD, FTIR, SEM, TG-DTA, TOC. The results showed that β-CDPU had been successfully grafted on the MP, and the β-CDPU coating didn’t change the crystal form of MP. The composite microsphere was a porous material, in which the mass fraction of β-CD was about 14.0%~17.2%, according to TOC analysis.A new attempt to study the β-CDPU/MP adsorption properties was carried out. Corilagin, a bio-active polyphenolic compound was selected as a model molecule, and the feasibility that the cyclodextrin/magnetic composite microsphere acted as a magnetic adsorbent is evaluated as well. The result showed that β-CD formed 1:1 inclusion complex with corilagin, and the inclusion constant of the binary complex was 1.19×104 L/mol, revealing that there were good interactions between β-CD cavity and corilagin, and the inclusion complex was relatively stable. The data revealed that β-CDPU/MP adsorbing corilagin followed the Langmuir adsorption isotherm. The separation and enrichment of the natural products with β-CDPU/MP adsorbent was investigated, taking the effective component corilagin separated and enriched from Phyllanthus niruri L. as a practical example. The adsorbent was directly put into the ethanol crude extract to adsorb corilagin, and then corilagin was eluted with water, 20%(w/w) ethanol aqueous solution and 50% ethanol aqueous solution. The adsorption ratio of corilagin on β-CDPU/MP from crude extract was 63.6%, and the desorption ratio was 17.0%. As a comparison, the adsorption ratio on MP was 98.1%, but hardly eluted by organic solvent. It was because the magnetic core Fe3O4 directly contacted and formed stable complex with corilagin, which made physical desorption impossible.This paper designed to coat a silicon dioxide insulating layer on the magnetic core Fe3O4, and then the β-CDPU/SiO2/MP composite magnetic microsphere was synthesized. The characterization results showed that silicon dioxide layer had been successfully grafted on MP, and the β-CDPU conjuncted on the outer of the SiO2/MP particle. The coating of SiO2 and β-CDPU didn’t change the crystal form of MP. The mass fraction of β-CD in β-CDPU/SiO2/MP is about 6.8%~9.3% demonstrated by TOC analysis. Analogous to the adsorbent β-CDPU/MP, β-CDPU/SiO2/MP adsorbing corilagin also followed the Langmuir adsorption isotherm. The adsorption-desorption results showed that the adsorption ratio of corilagin by β-CDPU/SiO2/MP in crude extract was 65.2%, and the total desorption ratio was 41.0%. Compared with β-CDPU/MP, the desorption ratio significantly increased. The results demonstrated that the adsorbent β-CDPU/SiO2/MP achieved quick and efficient enrichment corilagin from P. niruri L. It is expected that the cyclodextrin magnetic composite microsphere as magnetic adsorbent would be a potential candidate for active natural products separation and purification.