Preparative Isolation and Separation of Catechins from Green Tea Powders
| Autor: | Yu-min Chang, 張愉敏 |
|---|---|
| Rok vydání: | 2006 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 94 Green tea (non-fermented) is a popular, no alcoholic beverage in the world, and it is recognized for its high content of tea polyphenols, in particular tea catechins. The four represented catechins of green tea are, epigallocatechin(EGC), epicatechin(EC), epigallocatechin gallate(EGCG), and epicatechin gallate(ECG). Nevertheless, epigallocatechin gallate(EGCG) is the most abundant and biologically active compound in green tea. Many researches in the past found that green tea polyphenols have physiological effects in anti-oxidant, anti-tumorgenic, anti-mutagenic, anti-pathogenic, anti-inflammation, and anti-fungus, etc. Many health foods and products containing green tea polyphenols are already in markets, such as toiletries, cosmetics, foods, and beverages.The objective of this study is to develop an efficient and scalable isolation and separation technique, from which tea catechins can be produced with high purity and high recovery using green tea powers as the raw material. The results show that, first, the purity of the four catechins was about 16.0% in the green tea powders analyzed by HPLC. In the first stage of isolation, the method of liquid-liquid extraction and the method of solid-phase extraction were included. For the liquid-liquid extraction method operated in a batch mode, the procedure is simple and easy to proceed. Under the optimal extraction conditions (water/oil ratio as 1：1, extraction temperature as 30℃ and extraction time as 2 hours), the purity of the four catechins was raised to be about 57.0% and recovery of the four catechins was about 70.0%. For the solid-phase extraction method operated in a continuous mode, the procedure is more complicated and tedious. Using the intermediate polar XAD-7 HP resins as the packing material and operated under the optimal adsorption and desorption conditions, the purity of the four catechins were raised to be about 45.4% and the recovery of the four catechins were 74.9%. In the second stage, four catechins were separated and purified directly from the concentrate after the first stage by using elution chromatography with a preparative C-18 column operated under an optimal elution condition (mobile phase compositions of Methanol/water (1% acetic acid)). EGC, EGCG+EC and ECG were about 48.0%, 70.0% and 60.0%, respectively, the recoveries of the four catechins were collected in three separated regions and their purities were about 80+%, and after five times injection (about 88.6 mg the concentrate injected), the yields of EGC, EGCG+EC and ECG were about 5 mg, 28mg and 1 mg, respectively. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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