In silico molecular docking studies of oxadiazole and pyrimidine bearing heterocyclic compounds as potential antimicrobial agents.

Microbial resistance is a major problem faced by the scientific community. It has created an urgent need to develop antimicrobial agents with novel structures and mechanisms of action. With this aim, a series of novel 1,3,4-oxadiazoles bearing 3,4-dihydropyrimidine heterocyclic motifs 4a-l were designed and synthesized. One-pot Biginelli synthesis is pivotal due to the use of readily available chemicals, shorter reaction time, and ecofriendly synthesis with a good yield. The structures of the synthesized molecules were characterized and confirmed by infrared, H nuclear magnetic resonance (NMR), C NMR, and mass spectroscopic techniques. The title compounds were screened against Gram-positive and -negative strains of bacteria and fungi using the Mueller-Hinton broth method. Compound 4d was found to be the most promising against Escherichia coli (12.5 µg/ml), whereas the same compound showed good activity against Staphylococcus aureus at a concentration of 50 µg/ml. Other compounds of the same series, 4c and 4h, displayed moderate activity against Streptococcus pyogenes at a concentration of 50 µg/ml. Furthermore, results of the antifungal activity tests revealed that compound 4i showed promising activity against all the strains of fungi, Candida albicans, Aspergillus niger, and Aspergillus clavatus, at concentrations of 100, 50, and 100 µg/ml, respectively. Molecular docking also showed that these compounds had a significant binding affinity (Glide docking score: -7.74 to -6.531) for DNA gyrase, engaging in a series of bonded and nonbonded interactions with residues lining the active site. The results of molecular docking study validated the experimental findings, thereby providing an initiation mark to optimize this motif using a structure-based drug design approach.