Identification of two metabolites of the cholinesterase reactivator HI-6 isolated from rat urine

Abstract Two metabolites, isolated from the urine of rats given the cholinesterase reactivator HI-6 intravenously, still contained quaternary nitrogen atoms and therefore could not be extracted from aqueous solutions by organic solvents. Both metabolites were isolated by preparative high performance liquid chromatography and were identified using mass spectrometry, gas chromatography, infrared spectrometry, ultraviolet spectrometry and proton nuclear magnetic resonance spectrometry. The structures were confirmed by in-vitro preparation of the compounds. Both metabolites contained 2-pyridone moieties. One had an intact pyridinium-aldoxime moiety, and therefore could still be therapeutically active. The excretion of unchanged HI-6 together with the two identified metabolites does not provide for a 100% mass balance, indicating that in the rat, other, as yet unidentified, metabolites must be formed.