Antioxidant action of sodium diethyldithiocarbamate: reaction with hydrogen peroxide and superoxide radical.

The oxidation of sodium diethyldithiocarbamate (DDC) by hydrogen peroxide or superoxide radicals has been investigated. Hydrogen peroxide oxidizes DDC, leading to the formation of a hydrated form of disulfiram, a dimer of DDC having a disulfide group. In equimolar conditions, the overall process appears as a first-order reaction (k = 0.025 +/- 0.005 s-1), the first step being a second-order reaction (k = 5.0 +/- 0.1 mol-1.1.s-1). No radical intermediate was observed in this process. In the presence of an excess of any of the reagents, the hydrated form of disulfiram transforms into different products corresponding to the fixation of oxygen by sulfur atoms or replacement of C = S group by ketone function, in the presence of an excess of hydrogen peroxide. Superoxide anions (produced by steady-state 60Co gamma-radiolysis) oxidize DDC, yielding similar products to those obtained with hydrogen peroxide with a maximum oxidation G-value of 0.3 mumol.J-1. The rate constant k(O2.- + DDC) is equal to 900 mol-1.1.s-1.