We compared levels of (ϩ)-catechin, (Ϫ)-epicatechin, and their metabolites in rat plasma and urine after oral administration. Rats were divided into four groups and given (ϩ)-catechin (CA group), (Ϫ)-epicatechin (EC group), a mixture of the two (MIX group) or deionized water. Blood samples were collected before administration and at designated time intervals thereafter. Urine samples were collected 0 -24 h postadministration. (ϩ)-Catechin, (Ϫ)-epicatechin and their metabolites in plasma and urine were analyzed by HPLC-mass spectrometry after treatment with -glucuronidase and/or sulfatase. After administration, absorbed (ϩ)-catechin and (Ϫ)-epicatechin were mainly present in plasma as metabolites, such as nonmethylated or 3Ј-O-methylated conjugates. In the CA and MIX groups, the primary metabolite of (ϩ)-catechin in plasma was glucuronide in the nonmethylated form. In the EC and MIX groups, in contrast, the primary metabolites of (Ϫ)-epicatechin in plasma were glucuronide and sulfoglucuronide in nonmethylated forms, and sulfate in the 3Ј-O-methylated forms. Urinary excretion of the total amount of (Ϫ)-epicatechin metabolites in the EC group was significantly higher than the amount of (ϩ)-catechin metabolites in the CA group. The sum of (ϩ)-catechin metabolites in the urine was significantly lower in the MIX group than in the CA group, and the sum of (Ϫ)-epicatechin metabolites in the MIX group was also significantly lower than in the EC group. These results suggest that the bioavailability of (Ϫ)-epicatechin is higher than that of (ϩ)-catechin in rats, and that, in combination, (ϩ)-catechin and (Ϫ)-epicatechin might be absorbed competitively in the gastrointestinal tract of rats.
It is possible that increases in HDL-cholesterol concentrations may contribute to the suppression of LDL oxidation and that polyphenolic substances derived from cocoa powder may contribute to an elevation in HDL cholesterol.
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