Anti/pro-oxidative properties of selected standard chemicals and tea extracts investigated by DNA-based electrochemical biosensor

A DNA-modified screen-printed carbon electrode and the [Co(phen)(3)](3+) complex as an electrochemical DNA marker were used for the evaluation of anti/pro-oxidative properties of alpha-tocopherol, beta-carotene, quercetin, kaempferol and myricetin, as well as various tea extracts. Reactive oxygen species were generated using a model cleavage mixture composed of 5x10(-7) M [Cu(phen)(2)](2+) as the catalyst, 1x10(-3) M ascorbic acid as the chemical reductant and air oxygen as the natural oxidant. The antioxidative activity of standard chemicals increases with their concentration, reaching a maximum where prooxidative behaviour becomes of importance. Antioxidative effects of tea exctracts varied with the temperature of their preparation. Similar results were obtained by the 2, 2'-diphenyl-1-picrylhydrazyl free radical method.