Quantification of an antitumor agent (copen) in rat plasma by liquid chromatography-electrospray ionization tandem mass spectrometry and its application in a preclinical pharmacokinetic study.

Copen is a derivative obtained from the structural modification of osthole, which inhibits tumoral proliferation in many tumor cell lines. A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established for the quantification of copen in rat plasma. After a simple sample preparation procedure by one-step protein precipitation with methanol, copen and bicalutamide (internal standard, IS) were chromatographed on a Zorbax SB-C18 (4.6×100 mm, 1.8 µm) column with a mobile phase consisting of methanol-5 mm ammonium formate water with 0.1% formic acid (80:20, v/v). MS detection was performed on a triple quadrupole tandem mass spectrometer in the multiple reaction monitoring mode with a positive eletrospray ionization source. The assay was validated in the concentration range of 51.58-20,630 ng/mL, with a limit of quantitation (LOQ) of 51.58 ng/mL. The intra- and inter-day precisions (relative standard deviation) were ≤3.21 and ≤11.3%, respectively, with accuracy (%) in the range of 94.66-102.1%. The method was fully validated in a study of the pharmacokinetics of copen (25 mg/kg) after intragastric administration in rats.