New Biphenyl-Based Bispyrazolines: Synthesis, Antimicrobial, and Docking Studies

In this study, a series of new bispyrazolines 8(a-f) have been prepared from the cyclization reactions of bischalcones 7(a-f) with phenyl hydrazine by refluxing under the alkaline alcoholic (KOH/EtOH) conditions. The O-alkylation reactions of hydroxyl substituted chalcone 6 with different 1,omega-dibromoalkanes in the presence of anhydrous potassium carbonate, tetrabutylammonium iodide, and dry acetone afforded the symmetrical new bischalcones 7(a-f) in good yields. Chalcone 6 was realized by using the Claisen-Schmidt reaction of m-hydroxyacetophenone with bipheny-4-carboxaldehyde. The various spectroscopic parameters such as IR, H-1-NMR, C-13-NMR, and ESI-MS have been thoroughly used for the structural interpretations of the newly prepared products. The in vitro antibacterial and antifungal activities of these compounds have been examined with the help of serial tube dilution method, and many of the tested products were found to be revealing the promising antimicrobial properties, which were evident from their minimum inhibitory concentration values. The molecular docking simulations of the synthesized substances have also been achieved to observe the structural association into the active site of the Escherichia coli FabH (PdB: 3IL9). Docking results of these compounds suggested that bispyrazoline 8b demonstrated the lowest binding energy that describes its higher stability into the pocket of E. coli. The excellent inhibitory activity of this bisheterocycle against E. coli FabH may be ascribed on the basis of hydrophobic and van der Waals interactions.