Simultaneous Determination of Baicalein and Baicalin in Human Plasma by High Performance Liquid Chromatograph-Tandem Spectrometry and its Application in a Food-Effect Pharmacokinetic Study.

Abstract

Baicalein is a flavonoid isolated from skullcap and it is likely to exist in plasma at a low concentration because of the extensive first-pass metabolism in vivo. The aim of our study was to develop and fully validate a sensitive and selective HPLC-MS/MS method for simultaneous determination of baicalein and its main metabolite baicalin (baicalein-7-O-β-glucopyranuronoside) in human plasma. Liquid-liquid extraction was used for pretreatment of plasma samples. The mobile phase consisted of aqueous phase A (0.5% formic acid in 3 mM ammonium acetate solution) and organic phase B (methanol-acetonitrile-formic acid, 50:50:0.5, v:v:v). Detection was performed on a triple-quadrupole tandem mass spectrometer using positive electrospray ionization. Quantification was performed by multiple reaction monitoring mode at m/z transitions of 271.1→123.1 for baicalein and 447.1→271.0 for baicalin, respectively. The calibration curve was linear over the range of 1~400 ng/mL (r(2)>0.99) for both baicalein and baicalin. The intra-day and inter-day precision values were below 6.84% for baicalein and 8.56% for baicalin at 3 quality control levels. The mean accuracy was 95.27 ~ 110.56%, 91.82 ~ 105.01% for baicalein and baicalin, respectively. Analytes were stable during sample storage and handling. The method was proved to be accurate and specific and was applied to a pharmacokinetic study of baicalein in healthy volunteers under both fasted and fed states.