title: Evaluation of the redox properties and anti/pro-oxidant effects of selected flavonoids by means of a DNA-based electrochemical biosensor.
abstract: Quercetin and rutin as well as catechin and epigallocatechin gallate were investigated, as widely distributed representatives of flavonols and flavanols, respectively, regarding their anti/pro-oxidant properties. The flavonoids are irreversibly oxidized at a dsDNA-modified screen-printed electrode within 0.368 to 0.449 V vs. SHE without binding to DNA. Using the DNA biosensor the detection scheme of a DNA prevention/degradation exploits the [Co(phen)(3)](3+) complex as an electrochemical DNA marker. Antioxidant activity of flavonoids was tested in a model cleavage mixture composed of 5 x 10(-7) mol L(-1) [Cu(phen)(2)](2+) as the catalyst, 1 x 10(-3) mol L(-1) ascorbic acid as the chemical reductant and atmospheric oxygen as the natural oxidant where reactive oxygen radicals are generated. The antioxidant activity increases with the concentration of flavonoids reaching a maximum where pro-oxidative behaviour becomes of importance. The pro-oxidant potency of flavonoids depends on the presence of atmospheric oxygen and follows the order quercetin>rutin>epigallocatechin gallate>catechin.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, 81237 Bratislava, Slovakia. labuda@chtf.stuba.sk
authors.forename: Ján
authors.initials: J
authors.lastname: Labuda
authors.forename: Miriam
authors.initials: M
authors.lastname: Bucková
authors.forename: L'udmila
authors.initials: L
authors.lastname: Heilerová
authors.forename: Stanislav
authors.initials: S
authors.lastname: Silhár
authors.forename: Ivan
authors.initials: I
authors.lastname: Stepánek
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods*; D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D005419:Flavonoids / Q000032:analysis / Q000737:chemistry*; D015394:Molecular Structure; D016877:Oxidants / Q000032:analysis / Q000737:chemistry*; D010084:Oxidation-Reduction; D011794:Quercetin / Q000032:analysis / Q000737:chemistry; D012431:Rutin / Q000032:analysis / Q000737:chemistry
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D016877:Oxidants; D012431:Rutin; D002392:Catechin; D004247:DNA; D011794:Quercetin; C045651:epigallocatechin gallate