Urinary excretion of catechin metabolites by human subjects after red wine consumption

Little is known about flavonoid metabolism and excretion in man. In the present study, the urinary excretion of a major flavonoid in wine, catechin, and its metabolites, were measured after nine human subjects each consumed 120 ml red wine (RW) on one day and de-alcoholized red wine (DRW) on a separate day. Both the RW and DRW contained 120 (SEM 3) micromol catechin (35 mg). GC-MS analyses of the trimethylsilylated derivatives of catechin and 3' and 4' methylcatechin were performed before and after hydrolysis of conjugates by beta-glucuronidase and sulfatase. Baseline urine samples collected prior to wine consumption contained 0.013 (SEM 0.005) micromol catechin and metabolites. During the 8 h period following consumption of RW and DRW, 6.6 (SEM 0.9) and 5.3 (SEM 0.6) micromol catechin and metabolites were excreted in 893 (SEM 94) and 740 (SEM 101) ml urine respectively. This corresponded to 3.0-10.3% of the dose after RW and 2.1-8.2% of the dose after DRW. The amount of catechin and metabolites excreted in urine was 20% higher after RW compared with DRW (P=0.06). Catechin in all urine samples was present as metabolites and there were no differences in the proportions of individual metabolites after RW and DRW. As with other flavonoids, the fate of most ingested catechin is not yet known.