Separation of epigallocatechin gallate from tea polyphenol by simulated moving bed chromatography

(-)-Epigallocatechin gallate (EGCG) was purified from tea polyphenol by a two-step simulated moving bed (SMB) chromatographic process with C18-bonded silica gel as stationary phase and a mixture of methanol and water as mobile phase, removing the more retained components firstly and the less retained components secondly. An open-loop 3-zone SMB approach was used, a gradient of solvent strength in zones I and II was formed by different methanol dosage in purge and desorbent solutions and pre-equilibration was reached by the elution at the end of zone III. Under the approximation including linear adsorption and ideal chromatographic model, the operating parameters of the simulated moving bed were selected according to the "triangle theory". In the first SMB separation, a solution of tea polyphenol with 55.5% purity of EGCG was used for feeding and a raffinate solution with 92.2% purity and 99.7% recovery of EGCG was obtained. The raffinate solution was concentrated for feeding in the second SMB separation and an extract solution with 97.8% purity and 99.8% recovery of EGCG was obtained.