Exploring the Antimicrobial Potential of 1,3,4-Oxadiazole Derivatives: Synthesis, Characterization, and Activity Against Clinically Significant Pathogens

Abstract

The 1,3,4-oxadiazole ring is a structurally stable and pharmacologically active scaffold widely explored in drug discovery. This study presents a practical synthetic approach for 2,5-diaryl-substituted 1,3,4-oxadiazole scaffolds and evaluates their antimicrobial and antibiofilm potential. A total of 14 novel compounds were synthesized and screened for antibacterial activity against four clinically relevant bacterial strains: Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212), Escherichia coli (NCTC 13846), and Salmonella enterica (RSKK 04059). Minimum inhibitory concentrations (MICs) were determined in micromolar (μM) ranges, and several compounds demonstrated promising antibacterial effects. Among them, compounds 11h and 11i were selected for further evaluation of antibiofilm activity. Both compounds significantly inhibited biofilm formation by S. aureus, E. faecalis, and S. enterica, even at concentrations below their MIC values. A dose-dependent inhibition profile was observed, indicating potential utility in targeting bacterial biofilms at low doses. Interestingly, no antibiofilm activity was observed against E. coli NCTC 13846; instead, biofilm formation appeared to increase at certain concentrations. In summary, the synthesized 1,3,4-oxadiazole derivatives, particularly 11h and 11i, exhibited promising antimicrobial and antibiofilm activities, indicating their potential as core scaffolds for the design of new therapeutic agents targeting resistant bacterial strains.