Synthesis and Characterization of Fe (III) Complexes of 8- Hydroxyquinolines and Their Antimicrobial Activity against Staphylococcus aureus and Multidrug-Resistant Staphylococcus aureus

Abstract

The emergence of multidrug-resistant bacteria, particularly Staphylococcus aureus and Acinetobacter baumannii, presents an urgent need for new antimicrobial strategies. This research focuses on the synthesis and characterization of novel Fe(III) complexes formed with structurally distinct 8-hydroxyquinoline derivatives: 4-methyl-8-hydroxyquinoline, 5-nitro-8-hydroxyquinoline (nitroxoline), and 7-chloro-5-nitro-8-hydroxyquinoline. The complexes were characterized by UV-Vis spectroscopy, FT-IR spectroscopy, elemental analysis, LC-MS, and single-crystal X-ray diffraction. Their antibacterial activity was evaluated against methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA, MRSA), vancomycin-intermediate S. aureus (VISA), and A. baumannii. Minimum inhibitory concentration (MIC) assays, colony-forming unit counts, intracellular reactive oxygen species (ROS) assays, resistance development studies, hemolysis assays, and checkerboard synergy tests were performed. Results demonstrated that the Fe(III) complexes significantly enhanced antibacterial activity compared to free ligands, primarily by disrupting bacterial iron homeostasis and inducing ROS production. The findings offer promising insights into developing Fe(III)-based antimicrobial agents to combat antibiotic-resistant bacterial infections.