Comparison of Quercetin Pharmacokinetics Following Oral Supplementation in Humans

The objective of the study was to investigate the absorption of quercetin aglycone in 18 healthy human subjects administered via the following oral carrier systems: suspension of quercetin (quercetin QU995 powder in Tang (R) and spring water), nutritional bars (First Strike (TM)), and chews (RealFX (TM) Q-Plus (TM)). Subjects were divided into 3 groups of 6 individuals each receiving 500 mg quercetin in one of the aforementioned formulations. Blood levels were monitored immediately pre- and for 32 h postadministration. The concentration of total quercetin in blood samples was determined by solid phase extraction followed by high-performance liquid chromatography analysis. Pharmacokinetic parameters were determined by noncompartmental modeling using Kinetica software. The C-max of quercetin was highest with RealFX (TM) Q-Plus (TM) Chews (1051.9 +/- 393.1 mu g/L) achieved within 3.3 h as compared to that for First Strike (TM) Bars (698.1 +/- 189.5 mu g/L in 2.3 h) and Tang (R) suspension (354.4 +/- 87.6 mu g/L in 4.7 h). The results showed no statistically significant difference in quercetin absorption among groups due to high variability within groups receiving quercetin from same dosage form. This study represents the first comprehensive evaluation of quercetin absorption from quercetin fortified oral food products at doses commonly used for quercetin supplementation.