Absorption and metabolism of quercetin glucosides after the Ingestion of onions by human volunteers

摘要

Epidemiological studies have shown an association between increased intakes of dietary flavonols and a reduced incidence of cardiovascular disease. Onions containing flavonols, were fed to human volunteers after which plasma and urine were collected and analysed over a 24 h period. Five flavonol metabolites, quercetin-3'-sulfate, quercetin-3-glucuronide, isorhamnetin-3-glucuronide, a quercetin diglucuronide and a quercetin glucuronide sulfate, were detected in plasma in quantifiable amounts togetherwith trace quantities of six other metabolites. The profile of metabolites excreted in urine was markedly different to that of plasma with many of the major urinary components, including quercetin-3'-glucuronide, two quercetin glucoside sulfates and a methylquercetin diglucuronide, being either absent or present in the bloodstream in only trace quantities. This is indicative of substantial phase II metabolism. Total urinary excretion of quercetin metabolites was 12.9 umoles which corresponds to 4.7% ofintake.