Disposition of quercetin and kaempferol in human following an oral administration of Ginkgo biloba extract tablets.

Ten adult volunteers with an average age 28 years were given a single oral dose of six tablets of Ginkgo biloba extract. Quercetin and kaempferol in different period of human urine were determined by using RP-HPLC. The results showed the elimination rate constant k and the absorption rate constant ka of quercetin were slightly more than that of kaempferol; and the absorption half-life (t(1/2a)), the elimination half-life (t(1/2)) and t(max) of quercetin were less than that of kaempferol, the differences were, however, not statistically significant. The mean values of ka were 0.61 h(-1) and 0.55 h(-1), t(1/2a) 1.51 h and 1.56 h, k 0.37 h(-1) and 0.30 h(-1), t(1/2) 2.17 h and 2.76 h, T(max) 2.30 h and 2.68 h for quercetin and kaempferol, respectively, which mean absorption and elimination of quercetin and kaempferol are 0.17% and 0.22%, respectively. Quercetin and kaempferol are excreted in the human urine mainly as glucuronides.