Antibacterial Activities of 5-Nitro-2-uryl and 5-Nitro-2-Imidazolyl Derivatives of 1,3,4-Thiadiazole

Abstract

Introduction: Nitrofurans and nitroimidazoles are broad-spectrum antimicrobial agents, which affect the microbial DNA. The aim of the present study was to evaluate the new derivatives of these two groups of antimicrobials against certain Gram-positive and Gram-negative bacterial strains. Materials and Methods: Seven new derivatives of nitrofurans and nitroimidazoles were synthesized, and 6.4 mg of each derivative was dissolved in dimethyl sulfoxide. Then, 8 serial dilutions (0.5, 1, 2, 4, 8, 16, 32, and 64 μg/ml) of each derivative was prepared using Muller-Hinton broth, and the minimum inhibitory concentration for each derivative was measured and compared to ciprofloxacin (standard). Results: All the derivatives had no antibacterial effects against Gram-negative bacteria (minimum inhibitory concentration > 64 μg/ml); only 2-(5-nitro-2-furyl)-5-(n-pentylsulfunyl)-1,3,4-thiadiazole exhibited mild antibacterial effects against Klebsiella pneumonia (minimum inhibitory concentration of 16-32 μg/ml). The antibacterial effects of the derivatives against Gram-positive bacteria also showed variations from complete inhibition of the growth of Staphylococcus epidermidis and Bacillus subtilis (minimum inhibitory concentration < 0.5 μg/ml) by 2-(5-nitro-2-furyl)-5-(n-buthylthio)-1,3,4-thiadiazole to no inhibition of S. epidermidis and streptococcus pyogenes. Conclusion: These compounds have weak antibacterial effects; only two derivatives showed antibacterial effects similar to that of the positive control.