A GC-SIM-MS method for the determination of butylidenephthalide in rat plasma and tissue: Application to the pharmacokinetic and tissue distribution study

Butylidenephthalide is one of the major active components isolated from Rhizoma Chuanxiong. This paper describes a simple, rapid, specific and sensitive method for the quantification of butylidenephthalide in rat plasma and tissue distribution using a liquid-liquid extraction procedure followed by capillary gas chromatography-selected ion monitoring mode-mass spectrometry (GC-SIM-MS) analysis. The calibration curves were linear over the concentration ranging from 0.02-10.0μg/mL (r > 0.99) for plasma samples and 0.18-7.25μg/g (r>0.99) for the tissue samples. The limit of quantification (LOQ) was 1.0μng/mL or 1.0μng/g (ten times signal/noise ratio). Within- and between-day precisions expressed as the relative standard deviation (RSD) for the method were 2.39-2.98% and 2.97-4.26%, respectively. The methods of recovery for all samples were greater than 80% at the low, medium, and high concentrations. The method has been successfully applied to a pharmacokinetics study in rats after an oral administration of Butylidenephthalide with a dose of 20.0μmg/kg. The main pharmacokinetic parameters obtained were Tmaxμ=μ(0.22±0.06) h, Cmaxμ=μ(3±1)μg/mL, AUCμ=μ(32±6) h·g/mL, and Kaμ=μ(8.5±0.8)/h. The results showed that the butylidenephthalide was easily absorbed. The concentrations of butylidenephthalide in rat kidney, lung, heart, and cerebellum were higher than those in other organs. To determine free fraction in serum, samples were filtered using ultrafiltration membranes with a molecular weight cut-off of 10,000 Da and extracted using liquid-liquid extraction. The extracts were evaporated and analyzed by GC-MS. The protein binding in rat plasma, human plasma, and human serum albumin were 83±4%, 94±3%, and 89±3%, respectively.