The Voltammetric Behavior of Superoxide Dismutase/Catalase Mimics

Abstract

The voltammetric behavior of the superoxide dismutase/catalase mimics [(N,N'-bis(salicylidene)ethylenediamine) Mn(III)]Cl (or salenMn(III) chloride) 1 and [(N,N'-bis(3-methoxysalicylidene)ethylenediamine)Mn(III)]Cl (or 3,3'-methoxysalenMn(III) chloride) 2 in acetonitrile is described. Both compounds show quasi-reversible one-electron reductions to the Mn(II) compound. Electroanalytical techniques are used to follow the reaction between superoxide and 1 and 2 and it is shown that it is the reduced Mn(II) compounds which scavenge superoxide. It is also shown that both compounds electrocatalytically generate superoxide in the presence of dissolved dioxygen. The rate constant for this reaction was determined for both compounds using microelectrode steady state voltammetry. A general reaction scheme for interactions between these compounds and both dissolved dioxygen and superoxide is proposed.

α-Lipoic acid and glutathione protect against the prooxidant activity of SOD/catalase mimetic manganese salen derivatives

“…We have recently reported the principal features of the redox chemistry for these compounds and their reactions with dissolved dioxygen and electrogenerated superoxide [47]. Under these same conditions we observed no effect in the presence of saturated EDTA and conclude that no decomplexation occurs.…”

“…The reason for the differences between the prooxidant activities of the two Mn-salens was not determined though we have demonstrated that the rate of superoxide production by 1 is approximately twice that of 2 [47]. This may relate to the aromatic substitution pattern as semiquinone formation can occur under oxidising conditions in vivo to weaken OÁ Á ÁMn interactions.…”

“…A dominant feature of the cyclic voltammogram is the principal reduction peak which we have shown is due to the one electron reduction of Mn(III) to Mn(II) [47]. There are no cathodic features for either ligand in the absence of the manganese entity therefore peak potential, peak width and peak current (at a given concentration) are sensitive indicators of metal decomplexion (Table 1).…”

“…The general method used for electrochemical analysis of Mn-salen species is given elsewhere [47]. Anhydrous acetonitrile (MeCN) and tetraethylammonium terafluoroborate (TEAT) were obtained from Aldrich and used as received.…”

Fluorimetric study of the pro-oxidant activity of EUK8 in the presence of hydrogen peroxide

“…The same authors found that besides the antioxidant activity, this metal-reduced form may behave as a pro-oxidant by forming superoxide in the presence of relatively high concentrations of dissolved oxygen (O'Hare et al 2003). Supporting evidence was provided by Vezin et al who successfully synthesized superoxide-generating Mn(II)-salen complexes designed for high DNA cleaving activity (Vezin et al 2002).…”