Strong Antibacterial Properties of Anion Transporters: A Result of Depolarization and Weakening of the Bacterial Membrane

The development of low molecular weight anionophores is an emerging topic in chemistry, as the need for these compounds increases with the continuous discovery of pathologies involving anomalies in anion transport processes. Development of new concepts to initiate anion imbalance in living cells while fighting multidrug-resistant bacteria is a paramount topic. In this study, three series of compounds including <i>N</i>,<i>N</i>′-diphenylethynylbenzyl benzimidazolium salts (<b>1</b> and <b>2</b>), 1,1′-(pyridine-2,6-diyl)­bis­(3-(4-(phenylethynyl)­benzyl)-1<i>H</i>-benzo­[<i>d</i>]­imidazol-3-ium) salts (<b>3</b>–<b>5</b>), and 1,1′-(pyridine-2,6-diylbis­(methylene))­bis­(3-(4-(phenyl ethynyl)­benzyl)-1<i>H</i>-benzo­[<i>d</i>]­imidazol-3-ium) salts (<b>6</b>–<b>8</b>) displaying high antimicrobial activity and low toxicity against human cells were designed, synthesized, and studied. The most potent compound displayed micromolar minimal inhibitory concentrations in different Gram-negative and Gram-positive bacteria, while its hemolytic activity remained around 10% or less, even after a prolonged period of exposure. The mechanism of action of these benzimidazolium salts on bacterial membrane was assessed by bioanalytical techniques including assays in model membrane liposomes, membrane depolarization studies, and scanning electron microscopy (SEM) in living bacteria.