| Summary: | 碩士 === 國立雲林科技大學 === 化學工程與材料工程研究所 === 97 === Green tea is a non-fermentative tea and contains high content of tea polyphenols, particular catechins. The four major compounds of catechins include epigallocatechin (EGC), epicatechin (EC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG). Among these four major compounds, epigallocatechin gallate (EGCG) is the most abundant and biologically active compound in green tea. The objective of this study is to develop an efficient and scalable separation and purification process, from which the major catechins can be produced with high purity and high recovery yield using green tea powers as the raw material.
The analytical results by HPLC show that the contents of the four major catechins were about 14% in total in the green tea powders. In the first stage, the liquid-liquid extraction method operated in a batch mode was used. The optimal extraction conditions were water/oil ratio as 1:1, extraction temperature as 30℃ and extraction time as 2 hours. The obtained contents of the four major catechins were raised to be about 61% in total and the recovery yield was about 74%.
In the second stage, the four major catechins were separated and further purified by using elution chromatography in preparative scale with the normal phase first and then followed by the reversed phase. In the first purification step, the preparative normal phase chromatographic separation was used. N-hexane/isopropyl alcohol (1% acetic acid) was used as the mobile phase, and about 74% purity of catechins was efficiently collected. In the mean time, caffeine was efficiently collected and the purity was about 84%. The injection volume was scaled-up to 10 mL. After repeating the above operations four times by injecting about 400 mg catechins extracts, about 266 mg of concentrated decaffeinated extracts were obtained. In the second purification step, the preparative reversed phase chromatographic separation was used. Methanol/water (1% acetic acid) mixture was used as the mobile phase, EGC, EGCG, EC and ECG were all efficiently collected one by one and the individual purity was about 43%, 82%, 82% and 80% respectively. The recovery yield of each of the four major catechins collected in the four separated regions was about 77+%. The injection volume was only able to be scaled up to 2 mL. After performing the above operations four times by injecting about 80mg decaffeinated extracts, about 6.17 mg EGC, 20.51 mg EGCG, 2.99 mg EC and 8.03 mg ECG were obtained.
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