Abstract

Synthesis, Structural Elucidation, and Evaluation of Antimicrobial Activity of 5-Ethoxy-2-Mercaptobenzimidazole Derivatives

Author(s):Alaa Alkhafaji, Zuhair Muhi-Eldeen, Elham Al-Kaissi, Najah Al-Muhtaseb, Tawfiq Arafat and Mohammad A Ghattas

Objective: The aim of this study was to design and synthesize new amino acetylenic 5-ethoxy-2-mercaptobenzimidazole derivatives as potential antimicrobial agents. Methods: New series of 5-ethoxy-2-{[4-(t-amino-1-yl) but-2-yn-1-yl] sulfanyl}-1H-benzimidazole derivatives were synthesized by Mannich reaction, and investigated for their antimicrobial activity. Their structural confirmation was confirmed using the EuroEA elemental analyzer, and by Bruker FTIR, 1H-NMR, 13C-NMR. The antimicrobial activity was evaluated in-vitro by agar diffusion method and broth dilution test. The minimum inhibitory concentration and the minimum bactericidal/fungicidal concentration were determined. Results: The IR, 1H-NMR, 13C-NMR and elemental analysis were consistent with the assigned structures. All new amino acetylenic 5-Ethoxy-2-mercaptobenzimidazole derivatives showed good antibacterial activity against Bacillus subtilis with minimum inhibitory concentration value of 31.25 μg/ml except 5-ethoxy-2-{[4-(2-methylpiperidin-1-yl) but-2-yn-1-yl]sulfanyl}-1H-benzimidazole which showed value of 250 μg/ml, 5-ethoxy-2-{[4-(2,6-dimethylpiperidin- 1-yl)but-2-yn-1-yl]-sulfanyl}-1H-benzimidazole showed excellent antifungal activity against Candida albicans with the lowest minimum inhibitory concentration value of 31.25 μg/ml. Conclusion: The antimicrobial results promoted our interest to carry out further structural modifications, to enhance both antibacterial and antifungal activities, and their selectivity.

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