In vitro cytotoxicity and antimicrobial evaluation of novel 24–28 membered Schiff base octaazamacrocyclic complexes of manganese(II): Synthesis, characterization, DFT and molecular docking studies

The development of novel metal-based molecular antibiotics is an effective strategy to combat the rising threat of cancer and microbial diseases. In this view, novel Schiff base octaazamacrocyclic complexes of Mn(II) were synthesized using 2:2 molar ratio of macrocyclic ligands derived from Schiff base ligand [L] and dicarboxylic acids. The synthesized compounds were characterized by infra-red, 1 H NMR, 13 C NMR, ESI-mass, UV–visible, EPR, and powder X-ray diffraction spectral studies, together with elemental (CHN) analysis, molar conductance, and magnetic susceptibility measurements. Calculations based on density functional theory (DFT) help in determining the stability of synthesized macrocylic ligands. Electronic spectra led to the assignment of an octahedral geometry to the synthesized macrocyclic complexes. In vitro cytotoxicity of macrocyclic ligands and their Mn(II) complexes was examined against three distinct cancerous cell lines, including HeLa, A549, and MCF7 cells. The observed IC 50 values for the tested compounds against cancerous cell lines demonstrate a relatively good level of cytotoxicity. Molecular docking of Schiff base macrocyclic ligands supported their cytotoxic potential against the tested cell lines. Moreover, the antimicrobial activity of the synthesized compounds was also evaluated against bacterial ( E. coli, B. subtilis ) and fungal strains ( C. albicans, F. oxysporum ). The results indicate that the macrocyclic Mn(II) complexes have more antimicrobial potential than macrocyclic ligands against tested pathogens.