Stability studies of bis(pyridiniumaldoxime) reactivators of organophosphate-inhibited acetylcholinesterase.
Relative stability studies of three organophosphate-inhibited acetylcholinesterase reactivators, 1-(2-hydroximinomethyl-1-pyridinium)-3-(4-carbamoyl-1-pyridinium)- 2-oxapropane dichloride (HI-6), 1,1'-methylenebis(4-hydroximinomethylpyridinium) dichloride (MMB-4), and 1,1'-trimethylenebis(4-hydroximinomethylpyridinium) dibromide (TMB-4) were carried out by semiquantitative TLC and NMR methods. TMB-4 appears to be the most, and HI-6 the least stable of the three compounds. The extent of hydrolysis of HI-6, MMB-4, and TMB-4 in 0.05 M, pH 7 phosphate buffer was approximately 50, 25, and less than 1%, respectively, after 20 d at room temperature. The hydrolysis products of HI-6 were identified by NMR and MS (electron impact) as 2-pyridinealdoxime, picolinamide, and isonicotinamide, whereas that of MMB-4 was identified as 4-pyridinealdoxime. The stability of these reactivators decreases with increasing pH. TMB-4 was stable under both neutral and basic conditions at room temperature. Deuterium exchange of the methylene protons of MMB-4 in D2O and of the protons at the 2- and 6-positions of the pyridinium ring of TMB-4 in NaOD/D2O were observed.[1]References
- Stability studies of bis(pyridiniumaldoxime) reactivators of organophosphate-inhibited acetylcholinesterase. Lin, A.J., Klayman, D.L. Journal of pharmaceutical sciences. (1986) [Pubmed]
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