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 mu M; IC50, 30 mu M; IC50, 43 mu M; IC50, 55 mu M; IC50, 74 mu M, respectively) when compared to BHT (IC50, 54 mu M). 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 x 10(-4) M which is similarly better than the specific inhibitor caffeine IC50 = 5.2 x 10(-4) M. (C) 2008 Elsevier Ltd. All rights reserved.