Abstract: AIM: A rapid, sensitive and highly selective liquid chromatography-tandem mass spectrometry method was developed and validated for simultaneous determination of quercetin, kaempferol and isorhamnetin in dog plasma.METHODS: Quercetin, kaempferol and isorhamnetin conjugates were hydrolysed chemically.The analytes were extracted from plasma samples by liquid-liquid extraction, separated on a Luna ODS-2 column (150 mm ×2.1 mm I.D., 5 μm particle size), and detected by tandem mass spectrometry with a Finnigan IonSpray ionization interface. The mobile phase consisted of 0.1 % aqueous formic acid (A)and gradient-grade acetonitrile (B).RESULTS: The calibration curves for quercetin, kaempferol and isorhamnetin were linear in concentration ranges of 0.5-100.0 ng/mL in dog plasma.The method has a lower limit of quantification (LLOQ)of 0.5 ng/mL for all the three flavonols.The intra-and inter-day precisions, expressed as the R.S.D., were less than 7.3 %, 6.2 % and 6.4 % for quercetin, kaempferol and isorhamnetin, respectively, and the recovery was more than 70 %, 66 %and 70 %, respectively.The application of this assay was examined in a preliminary pharmacokinetic study of quercetin, kaempferol and isorhamnetin in beagle dogs after oral administration of 6 Ginkgo biloba tablets.CONCLUSION: The present method was suitable for determining quetcetin, kaempferol and isorhamnetin in dog plasma.

Key words: quercetin, kaempferol, isorhamnet, HPLC-MS/MS, pharmacokinetics