| Abstract: | Peroxidatic oxidation of N-alkyl and sulfalkyl-substituted 4-aminopyrazolones (amidopyrine and metapyrine) is mediated by oxyperoxidase, whereas the oxidation of non-substituted 4-aminoantipyrine occurs via the classical peroxidase cycle, without oxyperoxidase accumulation. The free radicals formed at the first step of the oxidation cycle show a tendency for disproportionation and exchange. During catalysis in heavy water the oxidation of substituted aminopyrazolones is accelerated by plant peroxidase. This effect is due to the activation of the second oxidative state of the enzyme. Complete peroxidatic oxidation of amidopyrine results in the formation of several reaction products. The main product is not identified as dioxypyramidone formed via nonenzymatic peroxidatic oxidation. The oxidation of the indicator (azopyram) which represents an amidopyrine-aniline mixture results first in the formation of amidopyrine radicals. The reaction product (dye) is formed via the binding of these radicals to aniline radicals. The latter are predominantly formed via a nonenzymatic route during the reduction of the amidopyrine radicals by aniline. Similar to the formation of azopyram and the full oxidation of amidopyrine, this reaction is accompanied by the displacement of the substituents from the 4-amino group. |
