engleski

Search for new antimicrobials: spectroscopic, spectrometric, and in vitro antimicrobial activity investigation of Ga(III) and Fe(III) complexes with aroylhydrazones

The in vitro antimicrobial activity of Fe(III) and Ga(III) complexes with N'-(2, 3-dihydroxy- phenylmethylidene)-3-pyr- idinecarbohydrazide (H 2 L 1), N'-(2, 4-dihydroxy-phenyl-methylidene)-3- pyridinecarbohydrazide (H 2 L 2), N'-(2, 5-dihy- droxy-phenylmethylidene)-3-pyridinecarbohydrazide (H 2 L 3), N'-(2-hydroxy-3-methoxyphenyl- methylidene)-3-pyri- dine-carbohydrazide (H 2 L 4), N'-(2-hydroxy-4-methoxyphenylmethyl-idene)-3- pyridine-carbohydrazide (H 2 L 5), and N'-(2- hydroxy-5-methoxyphenylmethylidene)-3- pyridinecarbo-hydrazide (H 2 L 6) toward several Gram-positive strains of Staphylococcus aureus, a Gram-negative strain of Escherichia coli, and a yeast Candida albicans were investigated. Fe(III)- complexes do not possess antimicrobial activity against all tested strains at concentrations up to 10 mg mL –1 . Ga(III) com- plexes with dihydroxy derivatives showed selective activity, while the broadest range of antibacterial and antifungal activities was observed for complex with 2- hydroxy-3-methoxy-derivative, ligand H 2 L 5. In addition, the coordination properties of ligands H 2 L 1 –H 2 L 3 in solution were investigated by UV–Vis spectroscopy. The stability constants (logK) for Ga(III)-H 2 L 1:1 complexes in MeOH/H 2 O 1/1 at pH 2.52 were determined, and amounted to 5.8, 5.68, and 4.7, respectively. Detailed characterization of complexes was performed by high-resolution mass spectrometry. The fragmentation pathways for dimer [Fe 2 (L 1) 2 ] 2+ , [Fe(HL) 2 ] + , [Ga(HL 2) 2 ] + and adduct ions are given. The comparison with analogue Ga(III) and Fe(III) com- plexes with compounds H 2 L 4 –H 2 L 6 was made as well.

Gallium ; Iron ; Hydrazone complexes ; Coordination properties ; Mass spectrometry ; Biological activity

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