Study On Quercetin And Kaempferol Purification By Molecularly Imprinted Technology

Molecular imprinting technique (MIT) has emerged as an attractive synthetic approach to construct a polymer matrix with molecular recognition sites, which introduced in 1972 by Wulff and Sarhan. The molecular imprinting polymers (MIPs) involve co-polymerization of functional monomer molecules with cross-linking agents in the presence of template molecules to create three-dimensional network polymers. Removal of the template molecules yields vacant recognition sites complementing both chemically and sterically to the imprinting molecule structure. These recognition sites enable imprinted polymers to be the mimics of enzymes, receptors and antibodies for screening various kinds of compounds from a mixture with abundant interferences.Quercetin and kaempferol are typical active compounds of the Ginkgo Flavonoid Glycosides, possessing various bioactivities such as inoxidability, antiviral property, antitumor and adjusting immune function. Thus, the research on selective separation and extraction of Ginkgo Flavonoid Glycosides'active components shows significant application value. In this paper, the preparation of MIP involved bulk polymerization using quercetin and kaempferol as the template molecule separately under optimized polymerized conditions. And then, the imprinting polymers were characterized by SEM, FTIR and BET. In addition, the obtained polymers were evaluated by adsorption isotherms, dynamic curves and separation factor with respect to their selective recognition properties for template molecule. And the imprinting, recognition, mass transfer and adsorption mechanism of Flavonoid MIP were further discussed.The contents of this thesis include the following aspects:1 The influence of three synthetic conditions, such as functional monomer, reactant ratio and porogen, were investigated. The optimum conditions were as follows:4-vinyl pyridine (4-VP) as the functional monomer, Ethylene glycol dimethacrylate (EDMA) as the cross-linker, reactant ratio n(QUE):n(4-VP):n(EDMA)= 1:5:25, in the porogens of chIoroform(THM,5.5ml) and N,N-dimethylformamide(DMF,1.5ml). The polymerizations were reacted at 60℃for 24h.2 The results of FTIR, SEM and BET showed that MIP was denser with homogenous and well-distributed pores, and there were steric binding cavern as well as spatial arrangement of complementary functionality.3 Dynamic adsorption of quercetin molecular imprinting polymer indicated that the specific adsorption increased quickly and easily reached saturation in a short period of time (about 60 min). The adsorption isotherm experiments were conducted and the Scatchard model was employed to further analyze the binding isotherms, which revealed that the homogeneous binding sites form in the polymers. Apparent Maximal Combination Amount (Qmax) and Equilibrium Dissociation Constant (Kd) were calculated to be 3.875mg/g and 9.174mg/L, respectively. The result of selectivity study showed that the selectivity coefficient is 3.58 with respect to competition specie rutin.4 Kaempferol molecular imprinting polymer was prepared by bulk polymerization, using kaempferol as the template molecule,4-vinyl pyridine as the functional monomer, Ethylene glycol dimethacrylate as the cross-linker in the porogens of CHC13-DMF (3:1, V/V.) Afterwards, the synthesized polymer, kaempferol-MIP, was analyzed by FTIR and SEM. In addition, the adsorption properties and mechanism were studied. The experimental results showed that the kaempferol-MIP exhibited a favorable affinity for kaempferol, and the saturated capacity can reach to 3.983 mg/g. The Scatchard analysis reveals that there exists a class of homogeneous recognition sites in kaempferol-MIP within the range of certain concentration. The result of selectivity study showed that the selectivity coefficient is 3.24 with respect to competition specie rutin.