Talanta Talanta 43 (1996) 95-102 Studies on the formation of Cu(I1) and Ni(I1) complexes of 1,2-dihydroxy-9, lo-anthraquinone and lack of stimulated superoxide formation by the complexes Saurabh Das, A. Saha, P.C. Mandal * Nuclear Chemistry Dtaision, Saha Institute qf‘ Nuclear Physics. l/AF, Bidhannagar. Calcutta-700 064, India Received 24 February 1995; revised 15 July 1995; accepted 8 August 1995 Abstract Formation of Cu(II) and Ni(II) complexes of 1,2,-dihydroxy-9.10-anthraquinone (DHA) has been studied by the spectrophotometric method. Both the metals form stable complexes of the type [M(LH)J where LHH, represents DHA. The effective stability constant of the Cu(I1) complex is 5.135 x 1019 while that of the Ni(I1) complex is 3.446 x 1025.These complexes, unlike free DHA, do not catalyze the flow of electrons from NADH to molecular O2 through NADH dehydrogenase. K~JWW~S: 1.2-Dihydroxy-9,10-anthraquinone(DHA); Cu(II)-DHA; Ni(II)-DHA; Stability constant; Cardiotoxicity 1. Introduction Anthracyclines constitute an important class of chemical compounds. The presence of a quinone chromophore which acts as a mediator in electron transport processes in many living systems has prompted an extensive study of these compounds. Techniques such as spectrophotometry, fluores- cence studies and circular dichroism have been applied as probes [ 1 - 51 to understand the nature and chemical characteristics of such molecules. These compounds gained more importance with the discovery that they could be used as drugs in the treatment of cancer. Among the chemothera- * Corresponding author. Fax: (91)033-374-637. peutic drugs in use today, quinone anti-tumor agents such as daunorubicin and adriamycin are important [6- 131. However, the principal draw- back from which these drugs suffer is that they are cardiotoxic [14- 191 and should not be applied to patients for a prolonged period of time. These compounds are reduced to semiquinone [20-231 by enzymatic systems and then reoxidised by molecular oxygen to give superoxide radicals and other reactive oxygen species [24&26]. In fact these radicals are responsible for the anti-tumor activity and cytotoxic properties of these com- pounds. Earlier studies [27,28] have shown that formation of metal complexes with these drugs greatly influences the toxicity imparted by them. In fact, complexation of adriamycin and carmino- mycin by Fe(III) gives complexes which are less 0039-914Oj96/Sl5.00 C 1996 Elsevier Science B.V. All rights reserved SSDI 0039-9140(95)01720-8