Synthesis, Characterization, and Bioactivity Investigation of Novel Benzimidazole Derivatives as Potential Antibacterial and Antifungal Agents

A series of benzimidazole derivatives <b>6a</b>-<b>j</b> was designed and synthesized via the condensation of the corresponding o-phenylenediamine intermediates with formic acid. Antibacterial activity was evaluated in vitro using the agar well diffusion method against <i>Staphylococcus aureus</i>, <i>Bacillus cereus</i>, <i>Escherichia coli</i>, and <i>Klebsiella pneumoniae</i>, with nitrofurantoin (300 µg/mL) as the positive control. Antifungal screening was performed against <i>Aspergillus flavus</i>, <i>Penicillium duclauxii</i>, and <i>P. italicum</i> at 20 and 50 µg/mL, with Amphotericin B as the reference drug at the same concentrations. Most compounds exhibited moderate to good antimicrobial activity. MIC determination identified <b>6h</b> as the most active antibacterial agent (MIC = 5.0 µg/mL). The SEM analysis of bacteria treated with <b>6h</b> revealed marked morphological damage, including cell deformation and membrane disruption, supporting a bactericidal mode of action. Collectively, these results highlight benzimidazole derivatives as promising scaffolds for the development of broad-spectrum antibacterial and antifungal agents.