Antioxidant and DNA damage protecting activities of newly synthesized thiol bridged bis-benzimidazole derivative and its dicationic analogue

Two new types of bis-benzimidazole derivatives containing thiol group have been prepared and characterized. The compounds contain sulfur with imidazole ring show promising biological activities such as antioxidant, anticancer, antimicrobial and etc. The aim of this study was synthesis of benzimidazole derivatives which not only show antioxidant activity but also protect DNA from oxidative damage. Antioxidant activities of the synthesized compounds were investigated with DPPH and hydrogen peroxide radical scavenging assays. DNA nicking assay was applied to establish activity of compounds to protect plasmid DNA from Fenton's reagent radicals. Both compounds had antioxidant activity, however, activity of dicationic analogue was greater than well-known antioxidant Vit C. IC₅₀ values calculated according to DPPH method were 14.5 μM for dicationic analogue ( 2 ) and 57.5 μM for 1,2-bis(1-methyl-1H-benzod]imidazol-2-ylthio)ethane ( 1 ). In hydrogen peroxide scavenge assay IC₅₀ values of compounds were 638.6 μg/mL for 1,2-bis(1-methyl-1H-benzod]imidazol-2-ylthio)ethane ( 1 ), 398.9 μg/mL for dicationic analogue ( 2 ). Furthermore, dicationic analogue promised an effective DNA protection due to its positive charge interacting with negatively charged DNA. Also the high solubility of the dicationic analogue in water due to its positive charge could provide a great advantage in biological applications.