Amino acids conjugated quinazolinone-Schiff's bases as potential antimicrobial agents: Synthesis, SAR and molecular...

A series of amino acids conjugated quinazolinone-Schiff's bases were synthesized and characterized by analytical and spectroscopic methods. All the synthesized analogues (8-43) and the intermediates (1-7) were screened for their in vitro antibacterial and antifungal activities. In antimicrobial activity, compounds 12-16, 21-25, 30-34 and 39-43 showed excellent antibacterial activity which is better than the antibacterial standard Streptomycin. Compounds 15, 23-25, 30-34, 36 and 38-43 showed excellent antifungal activities which is more active than the reference antifungal drug Bavistin. Further, to understand the correlation of biological activity with that of drug-receptor interaction, molecular docking was performed on active site ofglucosamine-6-Phosphate (GlcN-6-P) synthase (PDB ID: 2VF5) which showed good binding profile. Molecular docking studies and Preliminary structure-activity (SAR) relationship revealed that the tryptophan and phenylalanine conjugated quinazolinones with electron donating groups (OH and OCH₃) were found to be excellent antimicrobial activities which is better than the glycine and alanine conjugated derivatives. This may be explained by the contribution of aromaticity and hydrophobicity of amino acids. Among the series, compounds 41 and 43 showed the highest docking scores for antimicrobial activity. The conjugation plays a major role in improving the biological activities of those compounds.