Abstract:
According to studies, illnesses caused by drug-resistant bacteria cause approximately
seven hundred deaths annually. Although several drugs are currently being developed
in response to this matter, it is reported that the majority of these drugs are simply derivatives of the current class of antibacterial drugs, and as a result, they will only provide a temporary solution because bacterial cells will eventually develop resistance to them as well. In this regard a completely new class of compounds that are somewhat unconventional and could also provide new pathways and modes of action that are not observed by the current class could be introduced. Researchers have demonstrated that metal complexes have a positive degree of anti-bacterial potency. The goal of this research work was to synthesize, analyse, and test antibacterial activities of Schiff base ligands denoted as 3N and 4N, based on the position of nitro group in the ligand, and their corresponding metal complexes. Schiff base ligands were synthesised through a condensation reaction between 4-nitrobenzaldehyde / 3-nitrobenzaldehyde and 2-amino-5-chlorobenzophenone to form 4N and 3N respectively. They were then complexed with Cu(II), Co(II), Fe(II), and Ni(II) metals and characterized by FTIR, 1H NMR, and ESI-MS. Metal complexes were denoted as Cu4N, Cu3N, Co4N, Co3N, Fe4N, Fe3N, Ni4N, and Ni3N. All metal complexes, except for Cu3N and Cu4N, could not be comprehensively characterized by 1H NMR due to their paramagnetic nature. According to FT-IR and NMR analysis, the "O" and "N" donor atoms of the Schiff base ligand took part in interaction with the metal (II) ions. The expected molecular formula of ligands and metal complexes were confirmed by relating their expected molecular weights with m/z values from ESI-MS data.
Gram-negative Escherichia coli and gram-positive Staphylococcus aureus were used
as test organisms to determine the antibacterial activity of the ligands and complexes.
The test was done through a broth micro dilution test to find the minimum inhibitory
concentration. When compared to their respective ligands, all metal complexes except
Ni4N, displayed significant activity against both strains. Furthermore, the complexes
were more active against gram-positive bacteria. This may suggest that these compounds’ mode of action could be selective towards gram-positive bacteria.
