Bioactive benzhydrazone derived Schiff base and its metal(II) complexes: Synthesis, characterisation, cytotoxicity, DNA binding/cleavage, antimicrobial and antioxidant activity

Abstract

Bivalent mononuclear transition metal complexes of cobalt, nickel, copper and zinc were synthesized from (E)-2-(1-(2-(2-hydroxybenzoyl)hydrazono)ethoxy)benzoic acid. The FTIR, 1H NMR, 13C NMR, HR-Mass, UV–Vis., EPR, Powder XRD and SEM analysis were employed to investigate the structural features of synthesized compounds. The spectral data confirmed the square planar geometry of the complexes. The EPR spectra of the Cu(II) complex supported the proposed geometry. Powder X-ray diffraction (PXRD) analysis and scanning electron microscopy (SEM) imaging revealed that the complexes consist of nano-sized grains exhibiting a polycrystalline structure. The in vitro antimicrobial efficacy of the compounds was evaluated against various bacterial and fungal strains using the well diffusion method. The in vitro antibacterial activity demonstrated that all synthesized compounds were biologically active, and Zn(II) complex exhibited the highest inhibitory activity against S. aureus (gram-positive bacteria). For antioxidant activity, the free ligand and its metal chelates were evaluated using the standard DPPH method, revealing that the Co(II) complex displayed least inhibitory concentration value (IC50 = 16 ± 2.3 μg/mL) indicating the highest antioxidant activity. DNA interaction studies showed intercalation between complexes and DNA, and the Cu(II) complex exhibited a higher binding affinity of 2.78 ± 0.34 × 105 M−1. The DNA cleavage ability of the compounds was assessed using gel electrophoresis, demonstrating the effective cleavage of the pBR322 plasmid DNA. The Schiff base and its complexes were subjected to an anticancer evaluation against the human breast cancer cell line (MCF-7) using the MTT assay method. The percentage cell inhibition of the compounds was calculated.