Hindawi Publishing Corporation BioMed Research International Volume 2013, Article ID 906912, 7 pages http://dx.doi.org/10.1155/2013/906912 Research Article Oxidative Stress and Antimicrobial Activity of Chromium(III) and Ruthenium(II) Complexes on Staphylococcus aureus and Escherichia coli Paulina L. Páez, 1 Claudia M. Bazán, 2 María E. Bongiovanni, 1 Judith Toneatto, 2 Inés Albesa, 1,3 María C. Becerra, 1,3 and Gerardo A. Argüello 2 1 Departamento de Farmacia, Facultad de Ciencias Qu´ ımicas, Universidad Nacional de C´ ordoba, X5000HUA C´ ordoba, Argentina 2 Instituto de Investigaciones en F´ ısico Qu´ ımica de C´ ordoba (INFIQC) CONICET-UNC, Departamento de F´ ısico Qu´ ımica, Facultad de Ciencias Qu´ ımicas, Universidad Nacional de C´ ordoba, Ciudad Universitaria, X5000HUA C´ ordoba, Argentina 3 IMBIV-CONICET, Instituto Multidisciplinario de Biolog´ ıa Vegetal, Ciudad Universitaria, X5000HUA C´ ordoba, Argentina Correspondence should be addressed to Gerardo A. Arg¨ uello; gerardoa@fcq.unc.edu.ar Received 30 April 2013; Revised 8 July 2013; Accepted 1 August 2013 Academic Editor: Brad Upham Copyright © 2013 Paulina L. P´ aez et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he prevalence of antibiotic resistance has resulted in the need for new approaches to be developed to combat previously easily treat- able infections. he main aim of this work was to establish the potential of the synthetic -diimine chromium(III) and ruthenium(II) complexes (where the -diimine ligands are bpy = 2,2-bipyridine, phen = 1,10-phenanthroline, and dppz = dipyrido[3,2-a:2  ,3  - c]-phenazine) like [Cr(phen) 3 ] 3+ , [Cr(phen) 2 (dppz)] 3+ , [Ru(phen) 3 ] 2+ , and [Ru(bpy) 3 ] 2+ as antibacterial agents by generating oxidative stress. he [Cr(phen) 3 ] 3+ and [Cr(phen) 2 (dppz)] 3+ complexes showed activity against Gram positive and Gram negative bacteria with minimum inhibitory concentrations (MICs) ranging from 0.125 g/mL to 1 g/mL, while [Ru(phen) 3 ] 2+ and [Ru(bpy) 3 ] 2+ do not exhibit antimicrobial activity against the two bacterial genera studied at the concentration range used. When ciproloxacin was combined with [Cr(phen) 3 ] 3+ for the inhibition of Staphylococcus aureus and Escherichia coli, an important synergistic efect was observed, FIC 0.066 for S. aureus and FIC 0.064 for E. coli. he work described here shows that chromium(III) complexes are bactericidal for S. aureus and E. coli. Our results indicate that -diimine chromium(III) complexes may be interesting to open new paths for metallodrug chemotherapy against diferent bacterial genera since some of these complexes have been found to exhibit remarkable antibacterial activities. 1. Introduction Since their discovery, antibiotics have played an important role in health care. However, the increasing emergence of antibiotic resistance among a variety of microbial pathogens stimulates intensive research eforts with the aim of identify- ing alternative therapeutic approaches [1]. he chemistry of metallic complexes with heterocyclic ligands has attracted the interest of both inorganic and bioin- organic chemists in recent years, and the ield of coordination chemistry of metallic complexes has undergone a remarkable growth during the past few decades and became a growing class of research [2]. his enormous growth is attributed to the synthesis of a large number and variety of synthetic ligands (chelates) which behave as coordinating agents for metal ions [3]. It is known that 2,2  -bipyridine and 1,10-phe- nanthroline chelators act as potential antitumor agents [4, 5] and several metal chelates possess antibacterial, antifungal, antiviral and anticancer activities. However, in several cases, it has been found that metal chelates have more antimicrobial activity than the chelating agents themselves [6]. he study of the chromium complexes in coordination chemistry is of great signiicance due to their various appli- cations in biological processes. In vitro studies have demon- strated that chromium in the proper ligand environment can lead to DNA damage, plasmid cleavage, and protein cleavage [7–9]. Some reports showed chromium complexes as the cause of oxidation of DNA by binding with guanine [10, 11].