Tissue Concentrations of Quercetin and Its Metabolite Isorhamnetin Following Oral Administration of Quercetin in Mice

Absorption, metabolism, and tissue concentrations of quercetin were examined and compared in mice and rats after oral administration of quercetin at 50 or 100 mg/kg. Quercetin was absorbed quickly in mice and reached maximum plasma concentration in I hr post-administration, and declined sharply after 4 hr. Plasma concentration of isorhamnetin, a major metabolite, also increased sharply, indicating rapid metabolic conversion, but elevated level was maintained longer than that of quercetin. Quercetin and isorhamnetin were found predominantly in glucuronide/sulfate-conjugate forms in both mice and rats. Tissue concentrations of quercetin and isorhamnetin in mice and rats were in the order of liver>kidney>spleen>plasma both 1 and 6 hr postadministration. These results show that quercetin is absorbed in mice after oral feeding and quickly metabolized into isorhamnetin as demonstrated in humans and other animal species. The results also can be used to explain various pharmacological activities reported in mouse models.