Rational design, synthesis, and evaluation of acridone-peptide based antimicrobial and Antifolate agents against methicilin-resistant Staphylococcus aureus, Bacillus subtilis and dihydrofolate reductase.

To conquer the antimicrobial resistance, here, we developed acridone-peptide based DHFR inhibitors. Small peptides or amino acids are coupled with acid acridone either through amide linkage or via an azole-based linker. These hybrids exerted their antibacterial activity through a dual mechanism involving membrane disruption and intracellular DHFR inhibition, compound 7 emerged as the most potent DHFR inhibitor (IC50 0.11 μM) and good antibacterial agent against methicillin-resistant Staphylococcus aureus and Bacillus subtilis. Moreover, it attained >10-fold selectivity over hemolytic activity which justify the moderate MIC values. Drug-like features were evaluated by physiological experiments including solubility, plasma and liver microsomal stability, hemolysis study, and ADME analysis. Fluorescence imaging depicts compound 7 able to stain bacterial cells, time-kill kinetic study reveals its bactericidal mode of inhibition and it also attains antibiofilm activity. Compound 7 binds with the enzyme in a competitive mode of inhibition and with excellent binding affinity. Molecular dynamics simulations were executed to provide critical insights into enzyme-ligand interactions and their conformational changes.