Determination of quercetin and kaempferol in human urine after orally administrated tablet of ginkgo biloba extract by HPLC.

A sensitive, simple and accurate method was developed for determination of quercetin and kaempferol in human urine by reversed phase high performance liquid chromatography. The urine samples were analyzed on C18 column. Quercetin and kaempferol were analyzed simultaneously with good separation. UV detector was set at 380 nm. There was a linear relationship between chromatographic area of analytes and concentration of analytes over the concentration range 1.638-81.90 and 1.872-93.60 ng/ml for quercetin and kaempferol, respectively. The recovery of the assay was 99.7+/-6.2 and 97.4+/-7.2% for quercetin and kaempferol, respectively. The within-day and between-day coefficients of variation were less than 9.7 and 16.5% (RSD), respectively. The limit of detection was 1.0 ng/ml for quercetin and 1.1 ng/ml for kaempferol. The limit of quantitation was 1.61+/-0.11 ng/ml (n=5) for quercetin and 1.85+/-0.11 ng/ml (n=5) for kaempferol. The method developed has been applied to determine quercetin and kaempferol after orally administrated tablet of Ginkgo biloba extract in human urine.