Simultaneous determination of levophencynonate and its metabolite demethyl levophencynonate in human plasma by liquid chromatography tandem mass spectrometry

•No method for simultaneous determination of LPH and DMLPH in biological matrices has been reported.•The method was sensitivity and selectivity, and was successfully applied to the pharmacokinetic study in Chinese healthy volunteers.•The sample preparation was convenient, simple and lower cost than liquid–liquid extraction.•The acquisition time of this method was 3.5 min for every sample.

A sensitive and convenient high performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) method was developed to determine levophencynonate and demethyl levophencynonate levels in human plasma simultaneously. Chromatographic separation was achieved on a SHIMADZU Shim-Pack XR C8 column and mass spectrometric analysis was performed by an API5000 mass spectrometer coupled with an electro-spray ionization (ESI) source in the positive ion mode. The MRM transitions of m/z 358.4 → 156.4 and 344.5 → 144.2 were used to quantify levophencynonate and demethyl levophencynonate, respectively. This analytical method was fully validated with specificity, linearity, lower limit of quantitation (LLOQ), accuracy, precision, stability, matrix effect and recovery. The linearity of this method were developed to be within the concentration ranges of 10–4000 pg/mL for levophencynonate and 25–8000 pg/mL for demethyl levophencynonate in human plasma. This method was used in a clinical study which was administrated with single oral dose for Chinese healthy subjects to investigate the pharmacokinetics of levophencynonate and demethyl levophencynonate.