Structural, Antimicrobial and in Silico Studies of Some Schiff Bases of Trans-paramethoxycinnamaldehyde Derivatives

Abstract

Three Schiff bases viz; 3,5-bis[(E)-[(2E)-3-(4-methoxyphenyl)prop-2-en-1-ylidene]benzoic acid (3,5-DA), 2-[(E)-[(2E)-3-(4-methoxyphenyl)prop-2-en-1-ylidene]amino]phenol (OAP) and [3-(4-methoxy-phenyl)-allylidene]-[2-(2-{2-[3-(4-methoxy-phenyl)-allylideneamino]-ethoxy}-ethoxy)-ethyl]-amine (TPMC/DDE) are reported. The Schiff bases were synthesized from the condensation reaction of trans-paramethoxycinnamaldehyde and the primary amines (3,5-diaminobenzoic acid, 2-aminophenol and 1,8-diamino-3,6-dioxaoctane respectively), in dry methanol. The synthesized Schiff bases were characterized using UV-Visible, Fourier transform infrared (FTIR), ¹H, and ¹³C NMR spectroscopies. The In vitro antimicrobial screening of the Schiff bases were carried out on gram-positive bacteria: (Staphylococcus aureus and Bacillus subtillus) and gram-negative bacteria: (Pseudomonasaeruginosa, and Escherichia. coli strain13) and against the fungi, Aspergillus niger and Candida albicans using the agar well diffusion method. The ligands 3,5-DA and OAP only showed activity against the fungus, Candida albicans with inhibition zone diameter (IZD) of 10 mm and minimum inhibitory concentrations (MIC) of 5.0 mg/mL and 3.0 mg/mL respectively. The ligand, TPMC/DDE also showed varying activity against the bacteria, Pseudomonas aeroginosa with an IZD of 8.0 mm and MIC of 7.5 mg/mL while Escherichia coli displayed inhibition with an IZD of 10.0 mm and MIC of 1.9 mg/mL. According to molecular docking studies, the binding affinity of the compounds towards two validated antibiotic and antifungal drug targets (DD-transpeptidase–DDPT and N-myristyol transferase-NMT) were in agreement to their observed in vitro antimicrobial activities. Moreover, their retrieved binding poses explained intermolecular forces behind the interactions that exist between the proteins and the ligands, a knowledge which is very useful in structural modification for activity optimization.