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Separation of epigallocatechin-3-gallate from crude tea polyphenols by using Cellulose diacetate graft

Hong ZHU, Peiyong QIN

《化学科学与工程前沿（英文）》 2011年第5卷第3期页码 330-338 doi: 10.1007/s11705-010-1104-6

摘要： This study demonstrates a new Cellulose diacetate graft -cyclodextrin (CDA- -CD) copolymer asymmetric membrane prepared by a phase inversion technique for the separation of (-)-epigallocatechin-3-gallate (EGCG) from other polyphenols in crude tea. The graft copolymer, CDA- -CD, was synthesized by prepolymerization of cellulose diacetate (CDA) and 1,6-hexamethylene-diisocyanate (HDI), which was then grafted with -cyclodextrin ( -CD). Surface and cross-section morphologies of the CDA- -CD membranes were analyzed by using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FT-IR) indicated that the -CD was grafted onto the CDA by chemical bonding. The influences of the HDI/CDA mass ratio and the catalyst mass fraction on the -CD graft yield were investigated. The optimum conditions of a HDI/CDA mass ratio of 0.35 g·g and a catalyst mass fraction of 0.18 wt-% produced a -CD graft yield of 26.51 wt-%. The effects of the -CD graft yield and the concentration of the polymer cast solution on the separation of EGCG were also investigated. Under optimum conditions of a -CD graft yield of 24.21 wt-% and a polymer concentration of 13 wt-%, the purity of EGCG increased from 26.51 to 86.91 wt-%.

关键词： (-)-epigallocatechin-3-gallate (EGCG) tea polyphenols CDA-β-CD

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Surface molecularly imprinted polymers for solid-phase extraction of (--)-epigallocatechin gallate from

Yunling Gao,Ying Hu,Kejian Yao

《化学科学与工程前沿（英文）》 2015年第9卷第4期页码 467-478 doi: 10.1007/s11705-015-1526-2

摘要： Surface molecularly imprinted polymers (SMIPs) have been synthesized to selectively determine (−)-epigallocatechin gallate in aqueous media. SMIPs were prepared using a surface grafting copolymerization method on a functionalized silica gel modified with -cyclodextrin and vinyl groups. The morphology and composition of the SMIPs were investigated by scanning electron microscopy, Fourier transform-infrared spectroscopy and thermogravimetric analysis. In addition, the molecular binding capacity, recognition properties and selectivity of the SMIPs were evaluated. The imprinted polymers were found to have a highly specific recognition and binding capacity for (−)-epigallocatechin gallate in aqueous media which is the result of the hydrophobic properties of the -cyclodextrin and the hydrogen-bonding interactions of methacrylic acid. The SMIPs were successfully employed as solid-phase extraction adsorbents prior to the HPLC determination of (−)-epigallocatechin gallate in toothpaste. The HPLC analysis had a linear dynamic range of 0.5–50.0 µg?mL with a correlation coefficient of 0.9998 and the recoveries ranged from 89.4% to 97.0% with relative standard deviations less than 4.8%. The limit of detection and limit of quantification were 0.17 and 0.33 µg?mL , respectively. The method provides a promising approach for the preparation of selective materials for the purification and determination of complex samples.

关键词： β-cyclodextrin (−)-epigallocatechin gallate surface molecular imprinting solid-phase extraction