Bioavailability and metabolic pharmacokinetics of rutin and quercetin in rats

Rutin and quercetin, a flavone glycoside and its aglycone, are the flavonoids most widely and abundantly present in herbs and plant The aim of this study was to characterize and compare the bioavailability and metabolic pharmacokinetics of rutin and quercetin in rats. Quercetin was administered intravenously (33 μmol/kg) and orally (165 μmol/kg), while rutin was administered only orally (328 μmol/kg) to rats. Blood samples were withdrawn via cardiopuncture at specific time points. An HPLC method was used to determine the concentrations of quercetin before and after hydrolysis using β-glucuronidase and sulfatase, respectively. The pharmacokinetic parameters were calculated using noncompartment model of WINNONLIN. The results showed that after intravenous administration of quercetin, 93.8% of the dose was circulating as its sulfates and glucuronides. After oral administration of quercetin, the glucuronides and sulfates of querectin were exclusively present in the bloodstream, whereas the parent form of quercetin was not detected. The oral absorption rate of quercetin was 53% compared to intravenous administration after dose correction. When rutin was orally administered, sulfates and glucuronides of quercetin were exclusively present in the bloodstream, whereas rutin and quercetin were not detected. Quercetin showed higher oral absorption rate than rutin. In conclusion, quercetin sulfates and quercetin glucuronides represent the major metabolites either rutin or quercetin was administered to rats.