A highly sensitive and rapid LC-MS/MS method for quantification of bexarotene in mouse plasma and brain tissue:...

Emerging evidence has suggested that bexarotene, a nearly 20-year-old skin cancer drug, may be a potential drug candidate to treat Alzheimer's disease (AD) and other neurodegenerative disorders. As described in this study, a highly sensitive and rapid method, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine bexarotene in mouse plasma and brain tissue, was established and validated for the first time. Single-step protein precipitation utilizing methanol solution (containing 0.05 % acetic acid) as precipitation agent was employed to prepare the samples of plasma and brain tissue. Chromatographic separation in gradient elution mode was conducted via an Agilent ZORBAX SB-C18 column (50 mm × 4.6 mm, 5 µm) employing methanol-ammonium acetate buffer (5 mM, pH adjusted to 4.6 with acetic acid) as mobile phase which flowed at 0.45 mL/min. The total run time was 6 min for each sample. Detection through mass spectrometric technique was operated by selected reaction monitoring (SRM) in negative electrospray ionization mode. The method was linear within the range of 10.0-15000 ng/mL for plasma and 10.0-600 ng/mL for brain tissue homogenate with the lower limit of quantification of 10.0 ng/ml. The plasma or tissue homogenate was only required 20 μL. The intra- and inter-day precision were less than 13.8 %, and the RE was between -7.4 % and 3.4 %. The method was applied to investigate the plasma pharmacokinetics and brain distribution of bexarotene in mice after being intragastrically administered with bexarotene at the dosage of 100 mg/kg. The results showed that both brain and plasma concentrations of bexarotene peaked at 1.0 h. Bexarotene was rapidly eliminated with a half-life of 2.0 h.