Effects of quercetin and rutin on serum and hepatic lipid concentrations, fecal steroid excretion and their antioxidant properties were investigated in rats by oral administration. No toxic symptom was observed even at the dose of 1.0 g/kg of quercetin or rutin. Serum and hepatic lipid concentrations and fecal steroid excretion was not influenced remarkably, but serum thiobarbituric acid reactive substances (TBARS) decreased dose-dependently with the administration of quercetin or rutin. The decrease of serum TBARS was significantly correlated with the increase of serum free flavonoids (p < 0.05-0.001). Serum flavonoid concentrations, especially free quercetin, were higher in rutin-administered rats than in quercetin-administered rats at doses of 1.0g/kg for 10 d (p < 0.05-0.001). When 1.0g/kg of quercetin or rutin was administered in a single dose, they remained in the blood as aglycone or their conjugates of quercetin and isorhamnetin, even three days after administration. Recovered flavonoids were only 0.13% and 0.89% in urine for 3 d and 0.03% and 0.13% in serum on day 3 by administration of quercetin and rutin, respectively. Thus, some part of the administered quercetin or rutin was metabolized and showed antioxidant property, but had no remarkable influence on serum or hepatic lipid concentrations or fecal steroid excretion in rats.
The Pharmaceutical Society of Japan