Design and synthesis of benzimidazole-based derivatives with antimicrobial activity: mechanistic insights into...

A novel series of benzimidazole-2-substituted phenyl alkane sulfonate derivatives (3a-r) was rationally designed and synthesized via condensation of substituted o-phenylenediamines with freshly prepared alkane sulfonate aldehyde-bisulfite adducts (2a-f). All compounds were evaluated for antimicrobial activity against Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus), Gram-negative bacteria (Acinetobacter baumannii and Providencia stuartii), and the fungal strain Candida albicans. Most derivatives displayed moderate to weak antibacterial activity. In contrast, compounds 3c and 3i demonstrated pronounced antifungal potency against C. albicans, exhibiting MIC values of 8.2 ± 1.84 and 9.8 ± 1.92 μg/mL, respectively, outperforming the reference drug Amphotericin B (MIC = 11.8 ± 0.41 μg/mL). Mechanistic investigations revealed significant intracellular reactive oxygen species (ROS) accumulation in treated fungal cells. Ergosterol supplementation assays resulted in increased MIC values, indicating that antifungal activity is primarily mediated through membrane disruption via ergosterol binding rather than inhibition of cell wall biosynthesis. Molecular docking studies showed favorable binding interactions of compounds 3c and 3i within the CYP51 active site, which were further validated by molecular dynamics simulations demonstrating stable ligand-protein complexes under near-physiological conditions. Generally, these findings identify benzimidazole-based sulfonate hybrids as promising antifungal candidates that exert their activity through ROS generation and ergosterol-associated membrane targeting.