Hindawi Publishing Corporation Bioinorganic Chemistry and Applications Volume 2009, Article ID 603651, 8 pages doi:10.1155/2009/603651 Research Article Synthesis, Characterization, and Biological Activity Studies of Copper(II) Mixed Compound with Histamine and Nalidixic Acid Egla Yareth Bivi´ an-Castro, 1, 2 Mercedes G. L ´ opez, 3 Mario Pedraza-Reyes, 4 Sylvain Bern` es, 5 and Guillermo Mendoza-D´ ıaz 1 1 Departamento de Qu´ ımica, Divisi´ on de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, 36050 Guanajuato, GTO, Mexico 2 Centro Universitario de los Lagos, Universidad de Guadalajara, Avenida Enrique D´ ıaz de Le´ on 1144 Col. Paseos de la Monta˜ na, Lagos de Moreno, 47460 Jalisco, JAL, Mexico 3 Departamento de Biotecnolog´ ıa y Bioqu´ ımica, Cinvestav-IPN Unidad Irapuato, Km.9.6 Libramiento Norte, Carr. Irapuato-Le´ on, 36500 Irapuato, GTO, Mexico 4 Departamento de Biolog´ ıa, Divisi´ on de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, 36050 Guanajuato, GTO, Mexico 5 DEP Facultad de Ciencias Qu´ ımicas, UANL, Guerrero y Progreso s/n, Col. Trevi˜ no, 64570 Monterrey, NL, Mexico Correspondence should be addressed to Guillermo Mendoza-D´ ıaz, mendozag@quijote.ugto.mx Received 7 February 2009; Accepted 2 March 2009 Recommended by Virtudes Moreno A mixed copper complex with deprotonated nalidixic acid (nal) and histamine (hsm) was synthesized and characterized by FTIR, UV-Vis, elemental analysis, and conductivity. The crystal structure of [Cu(hsm)(nal)H 2 O]Cl·3H 2 O(chn) showed a pentacoordinated cooper(II) in a square pyramidal geometry surrounded by two N atoms from hsm, two O atoms from the quinolone, and one apical water oxygen. Alteration of bacterial DNA structure and/or associated functions in vivo by [Cu(hsm)(nal)H 2 O]Cl·3H 2 O was demonstrated by the induction of a recA-lacZ fusion integrated at the amyE locus of a recombinant Bacillus subtilis strain. Results from circular dichroism and denaturation of calf thymus DNA (CT-DNA) suggested that increased amounts of copper complex were able to stabilize the double helix of DNA in vitro mainly by formation of hydrogen bonds between chn and the sugars of DNA minor groove. In vivo and in vitro biological activities of the chn complex were compared with the chemical nuclease [Cu(phen)(nal)H 2 O]NO 3 · 3H 2 O(cpn) where phen is phenanthroline. Copyright © 2009 Egla Yareth Bivi´ an-Castro et al. This 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. 1. Introduction Since Lescher and col. prepared the nalidixic acid in 1962 [1], the synthesis of new quinolones continues (Figure 1). First generation antibiotics of quinolone family are effective against gram-negative bacteria usually found in light urinary diseases [2]; examples of these drugs are Nalidixic acid, Oxolinic acid and Cinoxacin. The fluoroquinolones, second generation, like ciprofloxacin are also effective against gram- positive bacteria; they can be used in urinary, skin, or respiratory infections [3]. Levofloxacin and sparfloxacin are examples of third generation quinolones, also known as fluoroquinolones, but they are more effective against gram-positives organism. They are used in treatment of pneumonia, bronchitis, sinusitis, and gonorrhea infections. Fourth generation quinolones include the trovofloxacin with an effectiveness against anaerobic organism [4]. Quinolones inhibit the bacterial DNA synthesis [2], and there are several hypotheses to explain their mechanism of action. One of these hypothesis suggests the inhibition of subunit A of DNA-gyrase in presence of ATP [5–7]. Another hypothesis supports the existence of a cooperative bond between the quinolone–DNA–DNA-gyrase [8–11]. Also, it is suggested that quinolone may form coordination complexes with a transition metal ion present in the cytoplasm or with a metal biocomplex; this metal ion could be copper(II) [12].