Detection of antioxidative activity of plant extracts at the DNA-modified screen-printed electrode

A simple procedure for the voltammetric detection of antioxidative activity of plant extracts based on the protection from DNA damage at the electrode surface is reported. A disposable electrochemical DNA biosensor fabricated as a carbon-based screen-printed electrode modified by a surface layer of the calf thymus double stranded (ds) DNA was used as a working electrode in combination with a silver/silver chloride reference electrode and a separate platinum auxiliary electrode. The [Co(phen)(3)](3+) ion served as the dsDNA redox marker and the [Fe(EDTA)](-) complex with hydrogen peroxide under the electrochemical reduction of the iron atom were used as the DNA cleavage mixture. A remarkable antioxidative activity of phenolic antioxidants such as rosmarinic and caffeic acids as standards and the extracts of lemon balm, oregano, thyme and agrimony was found which is quite in agreement with an antiradical activity determined spectrophotometrically using 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical.