Separation of epigallocatechin-3-gallate from crude tea polyphenols by using Cellulose diacetate graft BoldItalic-cyclodextrin copolymer asymmetric membrane

Abstract

This study demonstrates a new Cellulose diacetate graft β-cyclodextrin (CDA-β-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-β-CD, was synthesized by prepolymerization of cellulose diacetate (CDA) and 1,6-hexamethylene-diisocyanate (HDI), which was then grafted with β-cyclodextrin (β-CD). Surface and cross-section morphologies of the CDA-β-CD membranes were analyzed by using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FT-IR) indicated that the β-CD was grafted onto the CDA by chemical bonding. The influences of the HDI/CDA mass ratio and the catalyst mass fraction on the β-CD graft yield were investigated. The optimum conditions of a HDI/CDA mass ratio of 0.35 g·g^-1 and a catalyst mass fraction of 0.18 wt-% produced a β-CD graft yield of 26.51 wt-%. The effects of the β-CD graft yield and the concentration of the polymer cast solution on the separation of EGCG were also investigated. Under optimum conditions of a β-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-%.

Keywords

(-)-epigallocatechin-3-gallate (EGCG) / tea polyphenols / CDA-β-CD

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