Abstract
[Ag(HL)NO3] complexes (1-4) were obtained with (E)-N’-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)acetohydrazide (HL1); (E)-N’-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)benzohydrazide (HL2); (E)-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)hydrazinecarbothioamide (HL3) and (E)-N-methyl-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)hydrazinecarbothioamide (HL4) secnidazole-derived Schiff bases. In addition, complexes [Bi(HL3)Cl3] (5) and [Bi(HL4)Cl3] (6) were also prepared. The silver(I) complexes (1-4) showed antifungal activity against Candida fungal strains while the uncomplexed ligands and the bismuth(III) complexes (5-6) were inactive, suggesting that the antifungal effects are probably due to the presence of silver. Although the Schiff base ligands and complexes (1-6) revealed to be inactive against Gram-positive and Gram-negative aerobic bacteria, all compounds exhibited potent antimicrobial effects against several anaerobic bacterial strains, indicating that their mode of action probably involves anaerobic bio reduction of the nitro group, with formation of metabolites which are toxic to the microorganisms. Electrochemistry studies showed that bio reduction of the nitro group is favored in complexes (1-6) in comparison to the free ligands, which might, at least in part, explain their increased antimicrobial effects.
Highlights
Thiosemicarbazones and hydrazones are compounds possessing a wide range of pharmacological applications as antitumor, antiviral, antiparasitic, antifungal and antibacterial agents.[1,2] Their metal complexes exhibit antineoplastic[3,4] and antimicrobial[5] activities, among others.Silver compounds are well known for their applications as antimicrobial agents
In a previous work[14] we reported the syntheses of thiosemicarbazones and hydrazones containing
Six reference strains of Gram-negative anaerobic bacteria were tested: Bacteroides fragilis (ATCC 25285), Bacteroides thetaiotaomicron (ATCC 23745), Bacteroides vulgatus (ATCC 8482), Bacteroides ovatus (ATCC 8483), Parabacteroides distasonis (ATCC 1945) and Fusubacterium nucleatum (ATCC 25586)
Summary
Thiosemicarbazones and hydrazones are compounds possessing a wide range of pharmacological applications as antitumor, antiviral, antiparasitic, antifungal and antibacterial agents.[1,2] Their metal complexes exhibit antineoplastic[3,4] and antimicrobial[5] activities, among others.Silver compounds are well known for their applications as antimicrobial agents. Antimicrobial Effects of Silver(I) and Bismuth(III) Complexes with Secnidazole-Derived Schiff Base Ligands These compounds and their copper(II) complexes proved to present antibacterial activity against anaerobic bacterial strains.
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