Spectrophotometric and electrochemical study of protolytic equilibria of some oximes-acetylcholinesterase reactivators

Newly synthesized oximes, mono and bis imidazole derivatives, which promise to be more effective acetylcholinesterase reactivators than standard antid otes used, were investigated by spectrophotometric and electrochemical meth ods. The electrochemical investigations confirmed the existence of overlapp ing equilibria, obtained by spectrophotometric methods. Dissociation consta nts of those oximes were also obtained by numerical treatment of overlappin g equilibria, using the Lavendberg-Marquardt least square method, and when compared with the same for some similar compounds, were found to be very ef fective acetylcholinesterase reactivators. The distribution of ionic forms of the investigated oximes, as a dependence of pH values, was calculated fr om the obtained values of dissociation constants. The results indicated tha t many oxime anions will be available at physiological pH 7.4 and a relativ e increased ability to reactivate inhibited acetylcholinesterase could be e xpected. (C) 1999 Elsevier Science B.V. All rights reserved.