Simultaneous determination of six flavonoids from Paulownia tomentosa flower extract in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous determination of six components including apigenin, quercetin, apigenin-7-O-β-D-glucoside, quercetin-3-O-β-D-glucoside, 3'-methoxyluteolin-7-O-β-D-glucoside, and tricin-7-O-β-D-glucopyranoside in rat plasma using formononetin as the internal standard (IS). The plasma samples were pretreated by a one-step liquid-liquid extraction with dichloromethane. The chromatographic separation was carried out on a ZORBAX SB-Aq column with a gradient mobile phase consisting of acetonitrile and 2mM aqueous ammonium acetate. All analytes and IS were quantitated through electrospray ionization in negative ion multiple reaction monitoring mode. The mass transitions were as follows: m/z 269.1→117.2 for apigenin, m/z 301.2→151.2 for quercetin, m/z 431.3→311.2 for apigenin-7-O-β-D-glucoside, m/z 463.2→300.2 for quercetin-3-O-β-D-glucoside, m/z 461.3→283.1 for 3'-methoxyluteolin-7-O-β-D-glucoside, m/z 491.3→313.1 for tricin-7-O-β-D-glucopyranoside, and m/z 267.2→252.2 for IS, respectively. All calibration curves exhibited good linearity with correlation coefficient (r)>0.995. The intra-day and inter-day precisions (RSD) at three QC levels were both less than 14.0% and the accuracies ranged from 89.8% to 113.8%. The extraction recoveries of six compounds ranged from 82.3% to 92.5%. The validated method was successfully applied to pharmacokinetic study of the six components in male rat plasma after oral administration of Paulownia tomentosa flower extract.