Reversed-phase ion-pair chromatography-diode array detection of the bispyridinium compound MB327: plasma analysis of a potential novel antidote for the treatment of organophosphorus poisoning

摘要

In the case of poisoning by organophosphorus nerve agents or pesticides, there is still a lack of pharmacological treatment of the cholinergic crisis selectively targeting the nicotinic acetylcholine receptor. Recently, the compound MB327 was identified as a potential novel lead structure to close this gap, thus demanding a quantitative assay for initial pharmacokinetic (PK) studies. MB327 is a salt consisting of the dicationic bispyridinium compound (BPC) 1,1 '-(propane-1,3-diyl)bis(4-tert-butylpyridinium) and two iodide counter ions. Due to the permanent positive charge of the BPC, an isocratic reversed-phase ion-pair chromatographic separation (RPIPC) was developed using heptanesulfonic acid as ion-pairing reagent and 45% v/v methanol as organic modifier (1mL/min). Selective UV-detection (230nm) was done by a diode array detector (DAD) for reliable, rugged, precise (RSD<7%) and accurate (96-104%) quantitative analysis of 50L swine plasma (linear range 1-1000 mu g BPC/mL plasma, lower limit of quantification 2 mu g/mL). During method validation, diverse parameters essential for the chromatographic process were investigated to generate van ' t Hoff, van Deemter and width plots allowing calculation of thermodynamic data like the distribution constant K (5.7 +/- 0.3), change in enthalpy, H-0: -23.66kJ/mol, and entropy, S-0: -65J/(mol*K). In addition, RPIPC-DAD analysis enabled calculation of molar absorptivities of the BPC, epsilon(230): 17400 +/- 1100L/(mol*cm), and iodide, epsilon(230): 9900 +/- 400L/(mol*cm), which determination was hampered by interference with each other in conventional cuvette UV-spectrophotometric measurements. Finally, the RPIPC-DAD procedure was applied to samples from an in vivo study of swine. Copyright (c) 2015 John Wiley & Sons, Ltd.