Development and validation of a LC-MS quantification method for the lantibiotic MU1140 in rat plasma

This study reports the first ever development and validation of a quantification method for a lantibiotic in plasma. This method was developed for the quantification of total MU1140 in Sprague Dawley rat plasma. The procedure involved acidification of plasma samples with formic acid followed by precipitation of plasma proteins using isopropanol, filtration, and analysis by RPLC-MS. The lantibiotic gallidermin was used as an internal standard (ISTD). The analyte and ISTD were eluted using a gradient of isopropanol and water, both acidified with 0.3% formic acid (v/v), at a flow rate of 250 microl/min. Positive electrospray ionization was utilized at the ion source and the analyte and ISTD were both detected by selected-ion monitoring (SIM). Total run time was 15 min. This method was validated for selectivity, sensitivity, linearity, recovery, accuracy, and precision. The method was shown to be selective, with a quantitative linear range of 0.39-100 microg/ml using 25 microl samples. The bias, intra- and inter-day percent relative standard deviation at all concentrations tested was lower than 15%. MU1140 mean extraction recovery was 96.1%. The analyte was shown to be stable to freeze/thaw and for short- and long-term storage. Extracted MU1140 was stable at 4 degrees C for over 5 days. This method was successfully applied to a preliminary pharmacokinetic study of intravenously administered MU1140 in Sprague Dawley rats. Overall, this method was shown to be applicable for quantification of MU1140 in plasma samples for the purpose of further MU1140 ADME or bioequivalence studies.