title: Glucuronidation of the green tea catechins, (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate, by rat hepatic and intestinal microsomes.
abstract: The flavonoids (-)-epigallocatechin-3-gallate (EGCg) and (-)-epicatechin-3-gallate (ECg) are major components of green tea and show numerous biological effects. We investigated the glucuronidation of these compounds and of quercetin by microsomes. Quercetin was almost fully glucuronidated by liver microsomes after 3 h, whereas ECg and ECGg were conjugated to a lesser extent (12.2 +/- 0.2 and 7.5 +/- 0.2%, respectively). The intestinal microsomes also glucuronidated quercetin much more efficiently than ECg and EGCg. Although the rates were lower than quercetin, intestinal microsomes exhibited higher activity on the galloyl group of ECg and EGCg compared to the flavonoid ring, whereas hepatic glucuronidation was higher on the flavonoid ring of EGCg and ECg compared to the galloyl groups. The low glucuronidation rates could partially explain why these flavanols are present in plasma as unconjugated forms.
authors.affiliation: Nestlé Research Center, PO Box 44, CH-1000 Lausanne 26, Switzerland.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Crespy
authors.forename: Nathalie
authors.initials: N
authors.lastname: Nancoz
authors.forename: Manuel
authors.initials: M
authors.lastname: Oliveira
authors.forename: Jörg
authors.initials: J
authors.lastname: Hau
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Courtet-Compondu
authors.forename: Gary
authors.initials: G
authors.lastname: Williamson
mesh_terms: D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D020719:Glucuronides / Q000096:biosynthesis; D007082:Ileum / Q000378:metabolism*; D066298:In Vitro Techniques; D007583:Jejunum / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D008861:Microsomes / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D011794:Quercetin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013662:Tea / Q000737:chemistry; D014535:Uridine Diphosphate Glucuronic Acid / Q000378:metabolism
chemical_list: D020719:Glucuronides; D013662:Tea; D014535:Uridine Diphosphate Glucuronic Acid; D002392:Catechin; C062669:epicatechin gallate; D011794:Quercetin; C045651:epigallocatechin gallate