Studies On The Isolation And Purification Technique Of Ester Catechins

Catechins are the primary components of tea polyphenols which are the principle part in the tea leaves(accounting for 70-80%), and are receiving increasingly attention from the scientific rasearchers because of their bioactivities such as anti-tumour, clearance of free radicals, caries-prevention and odour-depression. There are about 6 kinds of catechins monomers , in which epigallocatechin-3-gallate(EGCG) and epicatechin-3-gallate(ECG) have the highest pharma-activity so are in a high demand.In this thesis, tea polyphenols are used as the raw materials, and the macroporous adsorption resin as the column packings. Single factor tests, orthogonal experimental designs and variance analyses are applied to optimize the operation parameters for purifying ester catechins using HPD-600 macroporous adsorption resin. The results indicate that optimum eluting conditions are as follows: eluting rate: lBV/h(BV=bed volume);ratio of diameter to height of the chromatographic column: 3 : 30;eluting mode: water -10% alcohol-20% alcohol-45% alcohol and eluting volume: 4BV. Then effluent fractions are collected according to different ethanol concentrations respectively. Analysis by TLC indicates that EGCG exists in 10% effluent fraction and ECG in 45% effluent fraction. The purities of EGCG and ECG are 66.32% and 79.68% respectively in corresponding condensed parts. Furthermore, ethyl-acetate extraction technique is used to purify the two kind of ester catechin monomers, and the purities are increased to 77.71% and 82.03% respectively. The recoveies of EGCG and ECG are 78.0% and 82.9%.In this work, rather economic equipments have been adopted, and EGCG and ECG products of high content can be obtained by using single chromatographic sepration. The developed technology is simple and easy to control with the advantages of low operation cost, using safe and nonpoisonous solvent and obtaining products of rather high purity. The separation technique is easy to be industrialized.In addition, based on the experimental data, the adsorption characteristics of catechins have been investigated in case of using HPD-600 macroporous adsorption resins that are packed in the fixed bed, so as to provide the bases for engineering design. Influenses of dlution rate and height of bed on breakthrough curve are also studied. An adsorption model for catechins mass transfer through HPD-600 resin is proposed and the height of mass transfer zone and total mass transfer coefficient in different operation conditions are calculated.