Epimerization of Tea Catechins and O-Methylated Derivatives of (−)-Epigallocatechin-3-<i>O</i>-gallate: Relationship between Epimerization and Chemical Structure

Suzuki, M.; Sano, Mitsuaki; Yoshida, Risa; Degawa, Masakuni; Miyase, Toshio; Maeda‐Yamamoto, Mari

doi:10.1021/jf0210627

Cited by 65 publications

(44 citation statements)

References 18 publications

(26 reference statements)

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“…However, the catechins have been shown to epimerize at a much slower rate in solutions with a pH of less than 6. Thus, EDTA, which gives a pH of 5.5 in water, has been added to decrease the epimerisation of the tea catechins [39]. In addition, the epimerisation of catechins can be minimised by extracting dry tea with 50% v/v ethanol or with water at or below 801C [40].…”

Section: Stability Of Catechinsmentioning

confidence: 99%

Extraction and isolation of catechins from tea

Vuong

Golding

Nguyen

et al. 2010

J of Separation Science

139

102

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Tea is a major source of catechins, which have become well known for their antioxidant potential. Numerous human, animal, and in vitro studies have linked tea catechins with prevention of certain types of cancers, reduction of the risks for obesity, diabetes, and cardiovascular disease, and improvement of the immune system. Tea catechins are widely used in various neutraceuticals, pharmaceuticals, and cosmetics for either enhancing product shelf-life or for enhancing human health. Thus, the demand for catechins has increased considerably. Catechins have been extracted and isolated from tea leaves by numerous methods through several steps including: treatment of the tea leaves, extraction of catechins from teas into solvents, isolation of catechins from other extracted components, and drying the preparations to obtain catechin extracts in a powder form. This paper outlines the physical and chemical properties of the tea catechins and reviews the extraction steps of the various extraction methods, as a basis to improve and further develop the extraction and isolation of the tea catechins.

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Section: Stability Of Catechinsmentioning

confidence: 99%

Extraction and isolation of catechins from tea

Vuong

Golding

Nguyen

et al. 2010

J of Separation Science

139

102

View full text Add to dashboard Cite

show abstract

“…This is thought to be due to the difference in the stereochemistry: trans-forms, in general, are more stable than cis-forms. 13,[35][36][37][38][39][40][41][42][43][44][45][46] Thus, the optimized extraction conditions (''Sample preparation'' section) were tested on catechin and epicatechin standards.…”

Section: Preservation Of Catechins From Epimerization During Extractionmentioning

confidence: 99%

Determination of catechin diastereomers from the leaves of Byrsonima species using chiral HPLC‐PAD‐CD

et al. 2010

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When catechins are found in plant extracts, they are almost always identified as catechin and/or epicatechin probably due to stereoselectivity of the enzymes involved in the biosynthesis of these substances. However, the lack of reports regarding to ent-catechin as well as ent-epicatechin does not necessarily mean that these compounds have not been produced. In fact, most of the previous reports used chromatographic conditions not suitable for such separation. This article describes a simple and reliable analytical HPLC-PAD-CD method for simultaneous determination of catechin diastereomers both in infusions and extracts from the leaves of Byrsonima species. The direct separation of catechin, ent-catechin, epicatechin, and ent-epicatechin was obtained in normal phase by HPLC-PAD-CD using Chiralcel OD-H as chiral stationary phase and n-hexane/ethanol with 0.1% of TFA as mobile phase.

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“…The major catechins found in green tea leaf include epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC), catechin (C), gallocatechin gallate (GCG), gallocatechin (GC), catechin gallate (CG) 3,4 and O-methylated catechin derivatives. 5,6 Research on biotransformation and pharmacokinetics show that bioavailability and functions of various individual catechins are different and EGCG shows strong activity to control diseases, such as cancer. 2,7 The taste characteristics of various components of catechins and their effects on sensory quality differ.…”

Section: Introductionmentioning

confidence: 99%

Tea extraction methods in relation to control of epimerization of tea catechins

Liang

Dong

et al. 2007

J Sci Food Agric

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Effect of water temperature and ethanol concentration on epimerization and extractability of tea catechins was investigated. The results showed that epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) were partially epimerized into gallocatechin gallate (GCG) and catechin gallate (CG), respectively, when tea catechins extract was heated in water solution at 100• C for 2 h or dry tea was extracted in water at 100• C. The epimerization of the catechins was inhibited if the tea catechins extract was heated as solid powder and the dry tea was extracted in 50% (v/v) ethanol or in water at 80• C or below. When the dry tea was extracted in water, the extractability of catechins increased with the increase of extraction temperature up to 100• C, but there was no statistically significant difference in total catechins between 80• C and 100 • C. When teas were extracted using ethanol solutions, the highest extractability of total catechins was obtained in 50% (v/v) ethanol for dry tea and in 75% (v/v) ethanol for fresh tea leaf. In order to reveal the real profiles of tea catechins in teas to be tested, dry tea should be extracted in 50% (v/v) ethanol for 10 min, while fresh tea leaf should be extracted in 75% (v/v) ethanol for 10 min. For commercial extraction, temperature should be controlled at 80• C if water is used as the solvent.

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Epimerization of Tea Catechins and O-Methylated Derivatives of (−)-Epigallocatechin-3-O-gallate: Relationship between Epimerization and Chemical Structure

Cited by 65 publications

References 18 publications

Extraction and isolation of catechins from tea

Extraction and isolation of catechins from tea

Determination of catechin diastereomers from the leaves of Byrsonima species using chiral HPLC‐PAD‐CD

Tea extraction methods in relation to control of epimerization of tea catechins

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