Identification of the Major Antioxidative Metabolites in Biological Fluids of the Rat with Ingested (+)-Catechin and (-)-Epicatechin

Abstract

(+)-Catechin and (-)-epicatechin are known to be biologically effective antioxidants present in the human diet, particularly in wine and tea. We studied the metabolism of these compounds to elucidate the truly active structures in biological fluids by their oral administration to rats. Without any treatment with beta-glucuronidase and sulfatase, a pair of metabolites were detected at much higher concentrations in the plasma, bile, and urine than the originally ingested compounds. Each major metabolite found in the plasma at the highest concentration was excreted in both the bile and urine, and was purified from urine. Their chemical structures were established to be (+)-catechin 5-O-beta-glucuronide and (-)-epicatechin 5-O-beta-glucuronide by MS and NMR analyses. These glucuronide conjugates exhibited high antioxidative activities as superoxide anion radical scavengers like their parent compounds. It is concluded that (+)-catechin 5-O-beta-glucuronide and (-)-epicatechin 5-O-beta-glucuronide are the biologically active in vivo structures of the ingested polyphenolic antioxidants.

Modulators of amyloid protein aggregation and toxicity: EGCG and CLR01

“…On the other hand, other studies have reported a decrease in the antioxidant activity of methylated catechins [217]. one hour showed 100% stability [71].…”

MAPK signaling in neurodegeneration: influences of flavonoids and of nitric oxide

“…The resulting phenolic compounds may be absorbed. catechin, respectively [78]. In humans, increases in 3 -Omethyl-catechin, sulphate, and glucuronide metabolites in plasma were observed after consumption of either red wine or de-alcoholised red wine [56].…”

In Vivo Bioavailability, Absorption, Excretion, and Pharmacokinetics of [14C]Procyanidin B2 in Male Rats

“…Such microbial metabolites have been detected in the urine of rats in the free form (Gonthier et al, 2003a,b) and/or as mammalian conjugates produced by a combination of O-methylation, glucuronidation, and/or sulfation after absorption (Baba et al, 2001a(Baba et al, , 2002Gonthier et al, 2003b). It has been shown that some flavan-3-ol conjugates (e.g., the 5-␤-Dglucuronides) but not all (e.g., 3Ј-O-methyl) retain their in vitro antioxidant activity (Harada et al, 1999). However, it has been suggested that their transient occurrence and low concentrations in plasma, as well as relatively high redox potential compared with tocopherols and ascorbate, make it unlikely that their antioxidant properties explain any possible benefit to health and that alternative mechanisms should be sought and evaluated (Clifford, 2004).…”