Metabolism of Green Tea Catechins: An Overview
Green tea is one of the most popular beverages worldwide. Its major components include (-)-epicatechin ((-)- EC), (-)-epicatechin-3-gallate (ECG) (-)-epigallocatechin (EGC) and (-)-epigallocatechin-3-gallate (EGCG). It has demonstrated strong antioxidative, anti-inflammatory and anti-cancerous properties and attracted a great deal of interest over last several years. However, there is some discrepancy between the results from human pidemiological studies and cultured cell and animal models. Two reasons for its limited in vivo activities have been considered: metabolism and bioavailability. Recent studies have demonstrated that green tea catechins undergo methylation, glucuronidation and sulfation in in vitro systems and in animals and in humans. It has been also found that efflux transporters Pgp, MRP1 and MRP2 play roles in the absorption and excretion of green tea catechins. Several processes including intestinal metabolism, microbial metabolism, hepatic metabolism and chemical degradation have been found to be involved in the fate of green tea, and to be responsible for its low availability in animals, and most likely also in humans. Pharmacokinetics, absorption, distribution, drug metabolism and excretion properties of green tea provide a better understanding for its in vivo activities. In this article, drug metabolism and microbial metabolism of green tea catechins in in vitro systems and in animals and in humans will be reviewed. It also covers the factors affecting their biotransformation and bioavailability: drug-drug inhibitory and inductive interactions of phase I and phase II enzymes, inhibition of non-drug-metabolizing enzymes, transporters, chemical instability, epimerization and interindividual variability.
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Document Type: Research Article
Affiliations: Metabolism and Pharmacokinetics, Novartis Institutes for BioMedical Research, 4560 Horton Street, Emeryville, CA 84568, USA.
Publication date: 01 October 2006
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- Current Drug Metabolism aims to cover all the latest and outstanding developments in drug metabolism and disposition. The journal serves as an international forum for the publication of timely reviews in drug metabolism. Current Drug Metabolism is an essential journal for academic, clinical, government and pharmaceutical scientists who wish to be kept informed and up-to-date with the latest and most important developments. The journal covers the following areas:
In vitro systems including CYP-450; enzyme induction and inhibition; drug-drug interactions and enzyme kinetics; pharmacokinetics, toxicokinetics, species scaling and extrapolations; P-glycoprotein and transport carriers; target organ toxicity and interindividual variability; drug metabolism and disposition studies; extrahepatic metabolism; phase I and phase II metabolism; recent developments for the identification of drug metabolites and adducts.