Synthesis, characterization, antimicrobial, antibiofilm, and molecular docking studies of Cu(II) and Zn(II) Schiff base complexes derived from L-tyrosine and indole-3-carboxaldehyde

Abstract

Schiff bases and their metal complexes have garnered significant interest as antimicrobial agents, particularly in addressing antimicrobial resistance (AMR). Schiff base-derived metal complexes constitute an important class of compounds that exhibit exceptional biological activity and are therefore promising candidates for drug development, especially in view of the growing threat of AMR and microbial biofilms. This study reports the synthesis and characterization of Cu(II) and Zn(II) complexes, and a Schiff base ligand derived from indole-3-carboxaldehyde and L-tyrosine. The structures of the ligand and its complexes were confirmed using IR, electronic, and NMR spectroscopy. Based on the experimental results, the Cu(II) and Zn(II) complexes were assigned square planar and tetrahedral geometries, respectively. The antimicrobial efficacy of the complexes was evaluated using disc diffusion and minimum inhibitory concentration (MIC) assays. Antibiofilm investigations and fluorescence microscopy revealed that both complexes were effective against P. aeruginosa biofilms, with the Cu(II) complex demonstrating notably greater activity than the Zn(II) complex. Computational studies were performed for target prediction and revealed strong binding affinities with specific P. aeruginosa proteins (PelA, LpxC, AlgL, ExoS, and PslG), thereby supporting the observed biological activity of the synthesized complexes. These synthesized Schiff base complexes efficiently disrupted biofilms, providing a promising approach for managing chronic infections associated with resistant bacteria.