Molecular docking, discovery, synthesis, and pharmacological properties of new 6-substituted-2-(3-phenoxyphenyl)-4-phenyl quinoline derivatives; an approach to developing potent DNA gyrase inhibitors/antibacterial agents.

Synthesis and molecular validation of 6-substituted-2-(3-phenoxyphenyl)-4-phenylquinoline derivatives (4a-h) as antibacterial/DNA gyrase inhibitors reported. Primarily, 6-substituted-2-(3-phenoxyphenyl)-4-phenylquinoline derivatives were docked into the active sites of DNA gyrase A&B, to ensure the binding mode of the compounds, and the results were superior on DNA gyrase A over DNA gyrase B. Based on this, S. aureus DNA gyrase A assay was proposed and executed. Most prominent DNA gyrase inhibition showed by 6-fluoro-2-(3-phenoxyphenyl)-4-phenylquinoline (4c), IC50 0.389μg/mL; 2-(3-phenoxyphenyl)-4-phenylquinolin-6-ol (4e), IC50 0.328μg/mL; and 5,7-dichloro-2-(3-phenoxyphenyl)-4-phenylquinolin-6-ol (4h), IC50 0.214μg/mL which were substituted with fluorine (4F), nitrile (4CN), hydroxyl group (4OH) and dichloro-hydroxyl (3,5Cl, 4OH) groups in the quinoline scaffold. Antimicrobial activity on Gram-ve bacteria Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 424), and Gram+ve bacteria Staphylococcus aureus (MTCC 96) and Streptococcus pyogenes (MTCC 442) was evaluated. Excellent antibacterial activity showed by S. aureus and S. pyogenes which indicates the activity dominance of 6-substituted-2-(3-phenoxyphenyl)-4-phenylquinoline derivatives on Gram+ve bacteria rather than Gram-ve. Subsequently, the cytotoxicity of 6-substituted-2-(3-phenoxyphenyl)-4-phenylquinoline derivatives was evaluated. Cytotoxicity results of MCF-7 (human breast cancer) and G361 (skin melanoma cancer) cell lines reveals that the 6-substituted-2-(3-phenoxyphenyl)-4-phenylquinoline derivatives are highly toxic to cancer cells. Predicted SAR, Lipinski's filter, Pharmacokinetic, and ADMET properties were also ensured the druggability probabilities of most favorable compounds among 6-substituted-2-(3-phenoxyphenyl)-4-phenylquinoline derivatives.