Quantitative analysis of a novel antimicrobial peptide in rat plasma by ultra performance liquid chromatography-tandem mass spectrometry

We described the first results of a quantitative ultra performance liquid chromatographytandem mass spectrometry method for a novel antimicrobial peptide (phylloseptin,PSN-1).Chromatographic separation was accomplished on a Waters bridged ethyl hybrid (BEH) C18 (50 mm × 2.1 mm,1.7 μm) column with acetonitrile-water (25∶75,v/v) as isocratic mobile phase.Mass spectrometry detection was performed in the positive electrospray ionization mode and by monitoring of the transitions at m/z 679.6/120,509.6/120 (PSN-1) and m/z 340.7/165 (Thymopentin,IS).Protein precipitation was investigated and the recovery was satisfactory (above 82%).The method was shown to be reproducible and reliable with intra-day precision below 5.3%,inter-day precision below 14.2%,and linear range from 0.02 to 2 μg/mL with r>0.994.The method was successfully applied to a pharmacokinetic study of PSN-1 in rats after intravenous administration.