Evaluation of in vitro antibacterial, DNA binding, DNA damage, DFT and antioxidant studies of aminobenzaldehyde-based heterocyclic Schiff base derivatives

Heterocyclic Schiff base derivatives have been synthesized through condensation of dimethylaminobenzaldehyde and various substituted amines in 1:1 molar ratio. Synthesized heterocyclic Schiff base derivatives (<bold>3a-3h</bold>) were structurally characterized by UV-visible, IR, H-1 and C-13 NMR spectroscopy, elemental analysis and mass spectrometry. Antibacterial property of heterocyclic Schiff base derivatives has been explored against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus using disk diffusion method. Results revealed that Schiff base derivatives <bold>3c, 3f</bold> and <bold>3h</bold> have significant antibacterial activity against tested bacterial strains. Heterocyclic Schiff base derivatives also explored for DNA binding interactions with calf thymus-DNA (Ct-DNA) by means of absorption spectroscopy, fluorescence measurements, circular dichroism, viscosity measurement and molecular docking study. Heterocyclic Schiff base derivatives <bold>3c, 3f</bold> and <bold>3h</bold> bind with Ct-DNA through groove mode with binding constant (K-b) 1.62 x 10(4), 1.58 x 10(4) M-1 and 2.3 x 10(4) M-1, respectively. Molecular docking of the target compounds was also carried out against B-DNA dodecamer d(CGCGAATTCGCG)(2.) Agarose gel electrophoresis study revealed that after the addition of compounds <bold>3c, 3f</bold> and <bold>3h</bold>, DNA damage induced by free radical has been inhibited. Antioxidant potential of heterocyclic Schiff base derivatives was also estimated by Diphenyl-1-picryl-hydrazyl (DPPH) free radical and hydrogen peroxide assay. The experimental results of the spectral properties of the synthesized derivatives <bold>3c, 3f</bold> and <bold>3h</bold> in solution were interpreted at the molecular level with aid of the DFT and TD-DFT/CAM-B3LYP/6-31 + G(d) computational methods with Becke-3-Lee-Yang-Parr(B3LYP) exchange-correlation functional approach.