Acetylcholinesterase Inhibitory Co(II), Fe(II), Pd(II) and Ru(II) Complexes of a Tinoridine-based Schiff Base:...

In recent bioinorganic research, Schiff bases and transition metal complexes have attracted considerable attention owing to their low toxicity and enhanced biological activities. In this study, Co(II) and Fe(II) complexes of the newly synthesized Schiff base ligand were characterized using FT-IR spectroscopy, elemental and thermogravimetric analyses, molar conductance, magnetic susceptibility, ultraviolet-visible (UV-Vis) and mass spectrometry (MS). The combined spectroscopic, magnetic, and analytical data were consistent with high-spin octahedral coordination environments for the Co(II) and Fe(II) complexes, and the Schiff base ligand was tentatively assigned as a tridentate ONO donor coordinating through the azomethine nitrogen, carbonyl oxygen, and benzyloxy oxygen atoms. The enzyme inhibitory and antioxidant activities of the Schiff base ligand and its Co(II), Fe(II), Pd(II), and Ru(II) complexes were evaluated. For the first time, a systematic comparison of the biological activities of structurally related Co(II), Fe(II), Pd(II), and Ru(II) complexes of the same tinoridine-derived Schiff base ligand was performed, allowing evaluation of the influence of the metal center on biological activity. All metal complexes exhibited significant acetylcholinesterase (AChE) inhibitory activity, with the Pd(II) complex displaying the highest potency. Furthermore, the Ru(II) complex demonstrated effective free-radical scavenging activity in the DPPH assay. These findings suggest that coordination of the Schiff base with transition metals enhances its in vitro biological activity and provides a basis for further biological and pharmacological investigations, including cytotoxicity and mechanistic studies.