International Journal of Science, Engineering and TechnologyAuthors: Ranjan Kumar, Niranjan Kumar Mandal
Abstract: The escalating threat of antimicrobial resistance necessitates the development of novel therapeutic agents with alternative mechanisms of action. This study reports the design, synthesis, and comprehensive characterization of a new hydrazide-oxime ligand, (E)-N'-(hydroxy(phenyl)methylidene) benzohydrazide (benzilmonoximehydrazide, H₂L), and its subsequent complexation with silver(I) and gold(III) ions. The compounds were synthesized in good yield and characterized using elemental analysis, molar conductivity, FT-IR, and NMR (¹H, ¹³C) spectroscopy. The analytical and spectroscopic data confirm the formation of the complexes, proposing a coordination polymer structure for the silver complex [Ag(L)]ₙ and a mononuclear square-planar geometry for the gold complex [Au(L)Cl]. The antimicrobial efficacy of the ligand and its metal complexes was evaluated in vitro against a panel of Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and fungal strains (Candida albicans, Aspergillus brasiliensis) using the agar well diffusion method. The results demonstrated that complexation significantly enhanced the bioactivity compared to the free ligand. Notably, the gold(III) complex exhibited superior, broad-spectrum antimicrobial potency, showing activity comparable to or exceeding that of standard reference drugs (Ciprofloxacin and Fluconazole) against several strains. This remarkable enhancement is attributed to the synergistic effect of chelation, which increases lipophilicity and cellular uptake, combined with the intrinsic biocidal properties of the noble metal ions. These findings position these complexes, particularly the gold derivative, as promising candidates for the development of new metalloantimicrobial agents to combat drug-resistant pathogens.
DOI: http://doi.org/10.5281/zenodo.17158158
