Design, Synthesis, and Biological Evaluation of β-Lactam Antibiotic-Based Imidazolium- and Pyridinium-Type Ionic Liquids

We herein report the preparation and investigation of antibacterial activity of biocidal ionic liquids (ILs) consisting of cationic imidazolium or pyridinium and an anionic β‐lactam antibiotic. The antibacterial properties were quantified by measuring the minimum inhibitory concentration and minimum bactericidal concentration against Escherichia coli O157:H7, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecium. In general, the ILs had improved antibacterial activity than their parent materials, whether individually or in combination. In 83% of the experiments, the ampicillin ILs (Amp‐ILs) had better antibacterial activities than their quaternary halide parent materials, whereas in 92% of the experiments, Amp‐ILs outperformed the commercially available sodium ampicillin salt. Amp‐ILs had up to 43 times improved antibacterial activity than sodium ampicillin. Overall, when normalized for ampicillin content, ILs had greater antimicrobial activity against E. coli O157:H7, K. pneumoniae, S. aureus, and E. faecium than sodium ampicillin alone. Antibacterial activities of novel β‐lactam antibiotic based imidazolium‐ and pyridinium‐type ionic liquids were studied. The ionic liquids generally demonstrated greater antimicrobial activity against both gram‐positive and gram‐negative microbesin comparison to sodium ampicillin salt, pyridinium or imidazolium halide, or the combined mixture of sodium ampicillin and quaternary halide