Abstract
Two salts of the mesoionic compounds 1,4-diphenyl-5-(5-nitro-2-furanyl)-1,3,4-thiadiazolium-2-thiol chloride (MC-1) and 4-phenyl-5-(5-nitro-2-furanyl)-1,3,4-thiadiazolium-2-phenylamine chloride (MC-2) were synthesized utilizing 1,4-diphenyl-thiosemicarbazide and 5-nitro-2-furoyl chloride as starting materials. Their structures were characterized by IR, 1H-NMR, 13C-NMR and elemental analysis. These compounds were analyzed for their influence on the effectiveness of norfloxacin, tetracycline, and erythromycin (standard antibiotics) against resistant strains of Staphylococcus aureus. MC-1 and MC-2, at sub-inhibitory concentrations of 16 μg/mL, favourably modulated the antibiotic activity of tetracycline by 16- and 32-fold, respectively (MIC), and that of erythromycin by 4-fold.
Highlights
During the last few years, mesoionic compounds (MCs) have attracted the attention of chemists because of the bonding aspects of their unusual structures, being mesomeric heterocyclic betaines, strongly stabilized by electron delocalization, and large dipole moments [1]
MC-1 is a thermodynamic product obtained under anhydrous conditions in a closed system and in the presence of pyridine while the kinetic product MC-2 is obtained under anhydrous conditions in a closed system
Hydrochlorides of the mesoionic compounds MC-1 and MC-2 effectively enhanced the antibiotic activity of tetracycline and erythromycin by reducing the concentrations needed to inhibit the growth of drug resistant strains
Summary
During the last few years, mesoionic compounds (MCs) have attracted the attention of chemists because of the bonding aspects of their unusual structures, being mesomeric heterocyclic betaines, strongly stabilized by electron delocalization, and large dipole moments [1] Due to their inherent structural characteristics, mesoionic compounds have aroused research interest in photonics, nonlinear optical studies [2,3,4,5,6,7,8] and medicinal chemistry, where a wide range of biological activities have been discovered, as summarized in several review articles [9,10,11]. The present findings indicate that 1,4-diphenyl-5-(5-nitro-2-furanyl)1,3,4-triazolium-2-thiol chloride (MC-1), and 4-phenyl-5-(5-nitro-2-furanyl)-1,3,4-thiadiazolium-2phenylamine chloride (MC-2), could serve as a source of heterocyclic compounds that modulate bacterial resistance, when used as adjuvants of antibiotics
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