Development of QSAR for antimicrobial activity of substituted benzimidazoles

Synthesis of New Fluoro-Benzimidazole Derivatives as an Approach towards the Discovery of Novel Intestinal Antiseptic Drug Candidates

In the present study, nineteen new fluoro-benzimidazole derivatives, including nifuroxazide analogs, were synthesized by microwave-supported reactions and tested against a panel of pathogenic microorganisms consisting of resistant strains. The synthesized compounds were characterized and identified by FT-IR, 1H- and 13C-NMR, mass spectroscopy, and elemental analyses, respectively. In vitro antimicrobial and cytotoxic effects of the synthesized compounds were determined by microdilution and by [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay. The compound 4-[5(6)-fluoro-1H-benzimidazol-2-yl)-N'-(2-methylbenzylidene)]benzohydrazide (18) showed particularly high inhibitory activity against the gastro-intestinal pathogens, such as Escherichia coli O157:H7, Escherichiacoli ATCC 8739, Escherichia coli ATCC 35218 and Salmonella typhimurium ATCC 13311 standard strains, with minimum inhibitory concentrations (MIC90) ranging from 0.49–0.98 µg/mL. The microbial panel contained a total of ten pathogens including Klebsiella sp., Mycobacterium sp., MRSA, etc., for which the level of inhibitory activity measured was higher than that exhibited by the tested concentrations (MIC > 1000 µg/mL). In vitro cytotoxicity results revealed that the inhibitory concentration (IC50) value (210.23 µg/mL) of compound 18 against CCD 841 CoN cells (human intestinal epithelial cell line) is about 430 times higher than its MIC90 value against the tested Escherichia coli strains. Furthermore, the docking study of compound 18 suggested that its structure is very compatible with the active site pocket of the phosphofructokinase-2 enzyme.

New Benzimidazole-1,2,4-Triazole Hybrid Compounds: Synthesis, Anticandidal Activity and Cytotoxicity Evaluation

Owing to the growing need for antifungal agents, we synthesized a new series 2-((5-(4-(5-substituted-1H-benzimidazol-2-yl)phenyl)-4-substituted-4H-1,2,4-triazol-3-yl)thio)-1-(substitutedphenyl)ethan-1-one derivatives, which were tested against Candida species. The synthesized compounds were characterized and elucidated by FT-IR, ¹H-NMR, ¹³C-NMR and HR-MS spectroscopies. The synthesized compounds were screened in vitro anticandidal activity against Candida species by broth microdiluation methods. In vitro cytotoxic effects of the final compounds were determined by MTT assay. Microbiological studies revealed that compounds 5m, 5o, 5r, 5t, 5y, 5ab, and 5ad possess a good antifungal profile. Compounds 5w was the most active derivative and showed comparable antifungal activity to those of reference drugs ketoconazole and fluconazole. Cytotoxicity evaluation of compounds 5m, 5o, 5r, 5w, 5y, 5ab and 5ad showed that compounds 5w and 5ad were the least cytotoxic agents. Effects of these two compounds against ergosterol biosynthesis were observed by LC-MS-MS method, which is based on quantification of ergosterol level in C. albicans. Compounds 5w and 5d inhibited ergosterol biosynthesis concentration dependently. A fluorescence microscopy study was performed to visualize effect of compound 5w against C. albicans at cellular level. It was determined that compound 5w has a membrane damaging effect, which may be related with inhibition of biosynthesis of ergosterol.