Determination and pharmacokinetics of chinensinaphthol methyl ether in rat urine by a sensitive and specific UFLC-ESI-MS/MS method

- A UFLC-ESI-MS/MS method was applied to determine CME in rat urine.
- A reliable and simple sample preparation method was optimized.
- The concentration-time and accumulation excretion curve was delineated.
- The pharmacokinetics of CME in rat urine after single oral dose was investigated.

A rapid, stable, and sensitive method based on ultra-fast liquid chromatography combined with electrospray ionization tandem mass spectrometry (UFLC-ESI-MS/MS) was established and optimized for quantification and pharmacokinetics analysis of chinensinaphthol methyl ether (CME) in rat urine. Samples were prepared by liquid phase extraction with ethyl acetate, and chromatographic separation was performed on an ACQUITY UPLC® BEH Phenyl column (2.1 × 50 mm, 1.7 μm). For gradient elution, we used a mobile phase consisting of water containing 0.1% formic acid and 5 mmol/L ammonium formate and methanol with 0.1% formic acid. The quantification was executed under multiple reaction monitoring (MRM) in positive mode. The precursor/product transition (m/z) in the positive ion mode was [M+H]+ m/z = 395.1 → 346.1. This method was validated by evaluating specificity, linearity, matrix effects, recovery, accuracy, precision, and stability, which were all shown to be reasonable and reliable. The lower limit of quantification (LOQ) was 0.5 ng/mL, and the linear range was 0.5-100 ng/mL. The method was successfully applied to quantify and analyze the pharmacokinetics of CME in rat urine. After oral administration of a single dose of CME (5.0 mg/kg), the accumulated amount of CME excreted in urine was 162.3 ± 54.1 ng, and the terminal elimination half-life was 53.4 ± 5.3 h, indicating low CME excretion in urine and significant CME metabolism in vivo.