Preparative separation and purification of epigallocatechin gallate from green tea extracts using a silica adsorbent containing beta-cyclodextrin

Abstract

A silica adsorbent containing beta-cyclodextrin (beta-CD) has been developed and used for the separation and purification of epigallocatechin gallate (EGCG) from the green tea extracts. The batch adsorption experiments demonstrated that, the beta-CD bonded silica adsorbent possessed excellent adsorption equilibrium capacity (>55 mg/g adsorbent) and adsorption ratio (>95%) for EGCG compared to the other tea catechins and caffeine. The excellent adsorption capacity and selectivity for EGCG are attributed to the specific interactions between beta-CD and EGCG. The preparative separation and purification performance of EGCG on the beta-CD bonded silica column (220 mm L x 15 mm id., 40-63 mu m) was then evaluated. The column was operated in the polar organic mode using methanol/acetonitrile/acetic acid as the mobile phase and eluted under a three-step gradient elution program. The sample was dissolved in acetonitrile and loaded on a preparative scale of about 0.8 mg/g adsorbent. Under the optimal chromatographic conditions, the target compound, EGCG, being the most retained species, was obtained at a purity of about 90% with a recovery of about 90%. The productivity of EGCG was about 6 mg per injection, which can be further increased by scaling-up the chromatographic system. (c) 2012 Elsevier BM. All rights reserved.