Liquid Chromatography-tandem Mass Spectrometry Method For Quantification Of Paclitaxel And Hydroxylated Metabolite In Rat Plasma And Tissues With Lithium Adduction

Background Paclitaxel is a natural anti-cancer compound extracted from the bark of the yew and widely used in the treatment of a variety of cancers. Some neutral compounds such as paclitaxel are difficult ionizated in the mass spectra. In order to improve the sensitivity, some special measures should be adopted.Objective To develop a liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the determination of paclitaxel and hydroxylated metabolite in rat plasma and tissues. The validated method should be applied to the pharmacokinetic and tissue distribution studies of rats after administration of albumin-bound (nab-)paclitaxel.Method A rapid, selective and sensitive liquid chromatography-tandem mass spectrometric method was developed and validated to determine paclitaxel and hydroxylated metabolite in rat plasma and tissues using lithium carbonate reagent and docetaxel as the internal standard (IS). The samples were separated by an Agilent XDB C8 column (150 mm×4.6 I.D., 5 μm). The mobile phase consisted of acetonitrile-10 mmol·L-1 ammonium acetate-100 mmol·L-1 lithium carbonate (60:40:0.1, v/v/v). The running time for each sample was 4.5 min. A tandem mass spectrometer equipped with electrospray ionization source was used as detector and operated in the positive ion mode. [M+Li]+was chosen as the parent ion for quantitative analysis. Quantification was performed using multiple reaction monitoring (MRM) of the transitions m/z 860→m/z 292 for paclitaxel, m/z 876→m/z 308+575+515 for 3’-p-hydroxypaclitaxel and m/z814→m/z 288 for the internal standard.Results The plasma linear concentration ranges of the calibration curves for paclitaxel and 3’-p-hydroxypaclitaxel were 1.0-8000 ng·mL-1 and 0.50-50.0 ng·mL-1, respectively. The lower limits of quantitation of paclitaxel and 3’-p-hydroxypaclitaxel were 1.0 ng·mL-1and 0.50 ng·mL-1, respectively. The tissue linear concentration ranges of the calibration curves for paclitaxel and 3’-p-hydroxypaclitaxel were 10.0-30000 ng·g-1 and 4.0-3000 ng·g-1, respectively. The methods were applied to evaluate test and reference albumin-bound paclitaxel formalatins in vivo pharmacokinetics and tissue distribution in rats. The pharmacokinetics of two formulations showed no significant difference, and had similar distribution characteristics.Conclusion A rapid, selective, and sensitive liquid chromatography-tandem mass spectrometric method was developed for the determination of paclitaxel and hydroxylated metabolite. Lithium adduct ion is suitable for the quantative and structural analysis of some neutral compounds for its stablility, high mass spectrometry response and low collision energy.