Synthesis and antioxidant properties of novel N-methyl-1,3,4-thiadiazol-2-amine and 4-methyl-2H-1,2,4-triazole-3(4H)-thione derivatives of benzimidazole class Original Research Article

Some novel 1-methyl-4-(2-(2-substitutedphenyl-1H-benzimidazol-1-yl)acetyl)thiosemicarbazides (16a–20a), 5-[(2-(substitutedphenyl)-1H-benzimidazol-1-yl)methyl]-N-methyl-1,3,4-thiadiazol-2-amines (17b–20b), and 5-[(2-(substitutedphenyl)-1H-benzimidazol-1-yl)methyl-4-methyl-2H-1,2,4-triazole-3(4H)-thiones (16c–20c) were synthesized and tested for antioxidant properties by using various in vitro systems. Compounds 16a–20a were found to be a good scavenger of DPPH radical (IC50, 26 μM; IC50, 30 μM; IC50, 43 μM; IC50, 55 μM; IC50, 74 μM, respectively) when compared to BHT (IC50, 54 μM). Noteworthy results could not be found on superoxide radical. Compound 19b, which is the most active derivative inhibited slightly lipid peroxidation (28%) at 10−3 M concentration. Compound 17c inhibited the microsomal ethoxyresorufin O-deethylase (EROD) activity with an IC50 = 4.5 × 10−4 M which is similarly better than the specific inhibitor caffeine IC50 = 5.2 × 10−4 M.