DNA interaction, SOD, peroxidase and nuclease activity studies of iron complex having ligand with carboxamido nitrogen donors

• Superoxide dismutase, peroxidase like activity of (Et3HN)[FeIII(bpb)Cl2] complex.
• DNA interaction as well as nuclease study of small molecule SOD mimic.
• Mechanism of nuclease suggest possible participation of reactive oxygen species (ROS).

Complex (Et3HN)[FeIII(bpb)Cl2], 1 {where H2bpb: N,N′-(1,2-phenylene)bis(pyridine-2-carboxamide)} was synthesized and characterized by reported procedure (Yang et al., 1991). Complex 1 was found to be effective in superoxide scavenging activity and an IC50 value of 4.1 μM was obtained in xanthine–xanthine oxidase nitro blue tetrazolium assay. Peroxidase-like activity of this complex was determined by the oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). DNA interaction studies of complex 1 showed binding of DNA through external or groove binding. Complex 1 exhibited chemical nuclease activity in the presence of hydrogen peroxide and cleaved supercoiled pBR322 DNA to its linear and nicked circular form at physiological pH. Mechanistic studies indicated possible role of hydroxyl radical (OH) species in DNA cleavage activity via hydroperoxo intermediate: [FeIIIOOH−]2+ → [FeIVO]2+ + OH.

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