Dipyridyl Azo Compound 4,4′-Azopyridine as a Potential Coating Material for Toilet Sanitizer

Good toilet hygiene can reduce the risk of pathogenic transmission. During flushing, pathogenic bacteria can be spread by the water droplets, especially in the toilet seat. Escherichia coli (E. coli) is one of the frequently occurring Gram-negative bacterial pathogens found in the toilet seats. In this study, we investigated the potential anti-E. coli activity of some azobenzene compounds. Among them, compound 2, with the heterocyclic nitrogen in both phenyl rings, showed the strongest antibacterial effect on E. coli, with the minimum inhibitory concentration of 80 µg/mL and the minimum bactericidal concentration of 320 µg/mL Compound 2 displayed a comparative zone of clearance [(14.50±2.29) mm] to that of ampicillin [(13.17±1.76) mm]. The reactive oxygen species (ROS) assay suggested that compound 2 might induce the loss of bacteria via the oxidative stress by eliciting the generation of intracellular ROS. We further examined the potential cytotoxicity of compound 2 to the human skin HaCaT cells. Compound 2-treated skin cells showed a good maintenance of cellular morphology and a clear definition of cell nuclei, with a satisfactory cell viability (ca. 90