Desenvolvimento e reatividade de Nitrosilo Complexos de Rutênio com possível ação antibacteriana

Abstract

The present work aims the development of new nitrosyl ruthenium complexes capable of acting as donors of nitric oxide in biological systems, since this molecule acts in a variety of physiological processes such as neurotransmission, blood pressure regulation and participation in the capacity of the immune system against tumor cells and intracellular parasites. For this reason, we present the synthesis, characterization, reactivity and antibacterial assays of cis-[Ru(bpy)(phen)(L)(NO)](PF6)3 type complexes where L are the TU= thiourea and 4-N-Imd = 4-nitroimidazole, bpy = 2,2'-bipyridine and phen = 1,10'- phenanthroline. The compounds were obtained from the cis-[Ru(bpy)(phen)Cl2] precursor complex in water and ethanol with addition of the ligands under study. By the UV-Vis technique, in aqueous media, it was possible to identify the MCLT bands for the polypyridine ligands as for the nitrosyl ligand at the 420-480 nm range. With respect to the infrared spectra, the complexes exhibited bands at 1926 and 1942 cm-1 assigned the to ѵ(NO+ ) with thiourea and 4-nitroimidazole, respectively, indicating the coordination of the nitrosyl ligand. The cyclic voltammograms obtained in 0.1 mol/L NaTFA and pH 3.5 showed E1/2 in 32 mV for the thiourea complex and 118 mV for the 4-nitroimidazole, both referring to the NO+/0 redox pair. Regarding the reactivity, the complexes showed to be able to release the nitric oxide by photochemical reduction and that the nitrosyl nitrite interconversion reaction occurs at pH 6.70 and pH 5.86 for the compounds with thiourea and 4-nitroimidazole, respectively. In addition, the antibacterial activity of the nitrosyl complexes was investigated against the bacteria Pseudomonas aeruginosa (ATCC-9027), Staphylococcus aureus (ATCC-25923- ATCC-00698) and Staphylococcus epidermidis (ATCC-12228-ATCC-35984) . The test revealed a MIC of 121.5 µmolL-1 for the thiourea complex against Pseudomonas aeruginosa (ATCC-9027) and a MIC of 511 µmolL-1 for this against Staphylococcus aureus bacteria (ATCC-25923/ATCC-00698) and epidermidis (ATCC-12228). This indicates that the compound under study has the ability to inhibit the growth of these bacteria. In addition, the compound showed a MBC of 511 µmolL-1 for Staphylococcus aureus (ATCC-25923) and Staphylococcus epidermidis (ATCC-35984) suggesting that this compound is an antibacterial agent.