Identification of Metabolites of (−)-Epicatechin Gallate and Their Metabolic Fate in the Rat

Abstract

After intravenous administration of (-)-epicatechin gallate to Wistar male rats, its biliary metabolites were examined. Deconjugated forms of (-)-epicatechin gallate metabolites were prepared by beta-glucuronidase/sulfatase treatment and purified by HPLC. Five compounds were subjected to FAB-MS and NMR analyses. These metabolites were shown to be (-)-epicatechin gallate, 3'-O-methyl-(-)-epicatechin gallate, 4'-O-methyl-(-)-epicatechin gallate, 4' '-O-methyl-(-)-epicatechin gallate, and 3',4' '-di-O-methyl-(-)-epicatechin gallate. After oral administration, five major metabolites excreted in rat urine were purified in their deconjugated forms and their chemical structures identified. They were degradation products from (-)-epicatechin gallate, pyrogallol, 5-(3,4-dihydroxyphenyl)-gamma-valerolactone, 4-hydroxy-5-(3,4-dihydroxyphenyl)valeric acid, 3-(3-hydroxyphenyl)propionic acid, and m-coumaric acid. Time course analysis of the identified (-)-epicatechin gallate metabolites showed that (-)-epicatechin gallate and its conjugate appeared in the plasma with their highest levels 0.5 h after oral administration; their levels rapidly decreased, and then they disappeared by 6 h. The degradation products, mainly in their conjugated forms, emerged at 6 h, peaked at 24 h, and disappeared by 48 h. In urine samples, (-)-epicatechin gallate and its methylated metabolites were hardly detected and the degradation products began to be excreted in the 6-24 h period, peaked in the 24-48 h period, and then began to disappear. The most abundant metabolite in both the plasma and the urine was found to be the conjugated form of pyrogallol. On the basis of these results, a possible metabolic route of (-)-epicatechin gallate orally administered to the rat is proposed.

Biotransformation of (−)-Epigallocatechin and (−)-Gallocatechin by Intestinal Bacteria Involved in Isoflavone Metabolism

“…celatus JCM 14811 were expected to have the potential to catalyze p-dehydroxylation of gallic acid and pyrogallol which are produced from galloylated catechins (EGCg, GCg etc.) and from gallic acid, respectively, by intestinal bacteria, 4,14,15) this was not the case (data not shown). In this connection, Wang et al 16) reported that Eggerthella sp.…”

Possible Evidence of Contamination by Catechins in Deconjugation Enzymes fromHelix pomatiaandAbalone entrails

“…To understand the beneficial biological activities of catechins, a tremendous amount of research has examined the absorption and metabolism of catechins, and deconjugation enzymes are often used in the experiments. [18][19][20] However, there is no report demonstrating that catechins were present in the deconjugation enzymes. This may be because in those studies, they dealt with the application C 3 10 5 10 EC 3 10 5 10 GC 3 10 5 10 EGC 3 10 5 10 Cg 3 10 2 5 ECg 3 10 2 5 GCg 3 10 5 10 EGCg 3 10 5 10 The detection limit was a signal-to-noise ratio of more than 3:1, and the quantification limit was a signal-to-noise ratio of more than 10:1.…”

Bioconversion of (−)-Epicatechin, (+)-Epicatechin, (−)-Catechin, and (+)-Catechin by (−)-Epigallocatechin-Metabolizing Bacteria

“…Particularly, in the last 5 years clarification on the catabolism of tea catechins by intestinal microbiota has been the focus of intense research interest because of poor absorbability of the intact catechins in the body relative to catechin catabolites. [6][7][8] We reported previously on the catabolism of +C and −EC by rat intestinal microbiota and proposed metabolic pathway of these catechins. 9) In addition to the above report, we have recently isolated and identified rat intestinal bacteria as −EGC-metabolizing bacteria and have reported their degradation abilities.…”