In Vitro Antifungal and Antioxidant Profiling of Binuclear Thiazole-based Schiff Base Metal Complexes

Abstract

The rapid emergence of multidrug resistance (MDR) among pathogenic microorganisms has become a major global health concern, creating an urgent demand for new and effective pharmacophoric systems. In this context, Schiff base ligands and their transition metal complexes have gained significant attention due to their structural versatility and promising biological activities. The present study investigates the in vitro antifungal and antioxidant activities of a thiazole-based Schiff base ligand, LA and its binuclear complexes with biologically relevant transition metal ions, namely Co(II), Ni(II), Cu(II), and Zn(II). The antifungal activity of the ligand and its metal complexes was evaluated against Aspergillus niger and Fusarium oxysporum using the mycelial growth inhibition method, while antioxidant potential was assessed through the DPPH free radical scavenging assay. The results clearly demonstrate that coordination of the Schiff base ligand with metal ions significantly enhances its biological performance. Among the investigated complexes, the Cu(II) complex exhibited the highest antioxidant activity, whereas the Ni(II) and Cu(II) complexes showed superior antifungal efficacy compared to the free ligand. The observed enhancement in activity is attributed to metal-induced modulation of redox behavior, increased lipophilicity, and improved interaction with biological targets. This study is particularly important for the scientific community as it establishes a clear link between the structural features of thiazole-based Schiff base metal complexes and their biological activities. By systematically evaluating multiple metal complexes, the work demonstrates how coordination chemistry can be strategically employed to improve antifungal and antioxidant efficacy, addressing the global challenge of MDR microorganisms. The findings provide valuable guidance for the design of novel metal-based therapeutic agents and Active Pharmaceutical Ingredients (APIs), while the correlation between metal type, structural properties, and biological performance contributes to advancing research in medicinal chemistry and bioinorganic chemistry.