engleski

Gallium(III) binding properties of aroylhydrazones derived from nicotinohydrazide

One strategy that has been explored to evade the bacterial resistance to drugs is to target the iron metabolism of bacteria, since iron is critical for all bacteria growth. Three major concepts have been evaluated to exploit limitations in the bacterial iron metabolism: reducing the availability of free iron with iron- chelating agents ; inhibiting iron metabolism in the infected host, and the “Trojan Horse strategy” which takes advantages of natural iron-uptake systems to deliver antimicrobial compounds inside the cells that then kill them [1]. Biological systems have difficulties to differentiate between Fe3+ and Ga3+ ions due to their nearly identical ionic radii, same charge, preferred coordination number and chemical behavior. However, Ga3+ lacks the redox activity of iron (3+/2+ redox chemistry) and the substitution of Ga3+ into metalloenzymes can result in a loss of enzymatic function, with cellular toxicity as a result, which has marked Ga3+ the “Trojan Horse” in biological systems. Recent studies have shown that biologically active salicylidene acylhydrazide is an excessively strong complexing agent for gallium and that chelation of Ga(III) to the hydrazone increase the stability of the compounds against acid-induced hydrolysis [2]. In this study we prepared structurally similar aromatic hydrazones (Scheme) and investigated their binding properties toward gallium(III) ions. Complexation was monitored in methanol/water 1/1 mixture by spectrophotometric batch titrations at pH = 2.52 due to ligands’ hydrolysis.

Gallium(III) ; aroylhydrazones

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