Synthesis and biological evaluation of some novel 1‐alkyl‐3‐methylimidazolium carboxylate ionic liquids as potential antifungal agents

Abstract

AbstractIn an effort to discover lead compounds that may be of importance as potent antifungal agents, a series of novel 1‐alkyl‐3‐methylimidazolium carboxylate ionic liquids were efficiently synthesized through a solvent‐free ultrasound‐assisted quaternization reaction of 1‐methylimidazole and alkyl bromides RBr (R = hexyl, octyl) followed by an anion exchange process with selected carboxylate anions (cinnamate, salicylate, crotonate, and oxalate). Quantitative yields obtained were in the range of 86–94%. Structure characterization was done using FT‐IR, 1H‐NMR, and 13C‐NMR spectroscopic techniques. All the synthesized compounds showed in vitro antifungal activity against the fungus Candida albicans with the minimum inhibitory concentrations found to be less than or equal to 1%. Preliminary cytotoxicity assays (trypan blue exclusion and MTT) were performed on all ionic liquids and findings revealed higher lymphocyte viability in 1‐hexyl‐3‐methylimidazolium carboxylate ionic liquids than in 1‐octyl‐3‐methylimidazolium counterparts. No extensive toxicity effect was observed with the carboxylate anion variation. Among the tested compounds, 1‐hexyl‐3‐methylimidazolium crotonate and 1‐hexyl‐3‐methylimidazolium oxalate exhibited the lowest cytotoxicity in the trypan blue exclusion and MTT assays, respectively. Together, our results highlight the potential of carboxylate‐based ionic liquids in the development of next‐generation antifungal drugs.