ELSEVIER Bioelectrochemistry and Bioenergetics 44 (1997) 31-35 Cyclic voltammetry and bioassay of some superoxide dismutase mimetic copper complex compounds v J. Labuda a,, L. Fen~ovfi b Z. Dura~:kovfi c 9 9 a Department of Analytical Chemistry, Slovak Technical University, 81237 Bratislava, Slovak Republic b Faculty ofPharmac); Comenius University, 83232 Bratislava, Slovak Republic c Department of Medical Chemisto; Biochemistry and Clinical Biochemistry, Comenius University, 81108 Bratislava, Slovak Republic Received 14 February 1997; received in revised form 30 May 1997 Abstract The redox behaviour of a copper(H) complex with the macrocyclic Schiff base ligand tetrabenzo [b, f, j, n] [1,5,9,13] tetraaza cyclohexadecine, TAAB, copper(II) bis(ethylenediamine) bis(salicylate) as well as four copper(H) complexes with N-salicylidenegluta- mate type Schiff bases and additional equatorial ligands such as pyridine, imidazole, thiourea and water has been investigated electrochemically at mercury drop and platinum disk electrodes. The half-wave potential values for the Cu(H)/Cu(I) redox couple obtained in aqueous solution as well as the reactions of the Cu(1) complexes with molecular oxygen and superoxide anion electrogener- ated in dimethyi sulfoxide are in agreement with the SOD-like activity of the complexes. Reaction mechanisms are discussed © 1997 Elsevier Science S.A. Keywords: Redox potential; Superoxide dismutase; Copper complexes; Reactive oxygen species; Bioassay; Macrocyclic ligands 1. Introduction Copper complex compounds are studied widely as structural and functional models of active centres of cop- per containing redox enzymes. Some copper complexes exhibit abilities of superoxide dismutase (SOD) and chemi- cal nucleases. In our previous papers [1-5] we have re- ported a SOD-like activity of various Schiff base ligand copper(II) complexes as well as the DNase mimetic activ- ity for a copper(II) complex with the macrocyclic Schiff base ligand tetrabenzo [b, f, j, n] [1,5,9,13] tetraaza cyclo- hexadecine, Cu(TAAB) 2+. With respect to the participa- tion of oxygen radicals in these processes, the reactivity of copper compoundg towards oxygen and superoxide anion is of great interest. The oresent paper deals with the cyclic voltammetry of the [Cu(TAAB)]CI2 complex, the bis(ethylenediamine) bis(salicylate) copper(II) complex, Cu(sal)2(en) 2, the cop- per(II) complex of N-salicylideneglutamate Schiff base ligand and pyridine, Cu(sal-o,L-glu)py, and three N-sali- * Corresponding author. Fax: +421-7-393198; e-mail: labuda@chtf.stuba.sk 0302-4598/97/$17.00 © 1997 Elsevier Science S.A. All rights reserved. PI! S0302-4598(97)00058-5 cylidene-L-ethyiglutamato copper(II) complexes, Cu(sal- L-etglu)X, where X is imidazole, thiourea or water molecule as an additional equatorial ligand (Fig. 1), in aqueous and DMSO media. In the [Cu(TAAB)]CI 2 and Cu(sal)2(en) 2 complexes, the copper atom is coordinated by four nitro- gen atoms in the equatorial plane similarly as it is in the enzyme Cu,Zn-SOD. An investigation of the redox behaviour of the com- plexes and the evaluation of their SOD-like activity to- wards the enzymatically produced superoxide anion were the aims of the study. As the electrochemistry can provide stable pure solutions of the O~- radical by means of the electroreduction of oxygen in aprotic media [6], the mecha- nism of the copper complexes/oxygen interactions was studied in dimethyl sulfoxide, DMSO. 2. Experimental The complex [Cu(TAAB)](NO3)2 was prepared at the Institute of Physical Chemistry, Ukrainian Academy of Sciences, Kiev, as described previously [7]. Its chloride analogue, [Cu(TAAB)]Ci 2, was prepared in our laboratory