title: Antioxidant activity of betanidin: electrochemical study in aqueous media.
abstract: The antioxidative mechanism of action of betalains is of significant interest because these pigments are recently emerging as highly bio-active natural compounds with potential benefits to human health. Betanidin, the basic betacyanin, comprises the 5,6-dihydroxyl moiety, which results in its high antioxidant activity. Oxidation of betanidin by voltammetric techniques and chro matographic identification of the oxidation products with spectrophotometric and mass spectrometric detection (LC-DAD-MS/MS) were performed. Two main oxidation peaks for betanidin are observable at pH 3-5. These peaks become merged at higher pH, suggesting a different mechanism of oxidation at higher and lower pH values. The low oxidation potential of betanidin confirms its very strong reduction properties. The presence of two prominent oxidized products, 2-decarboxy-2,3-dehydrobetanidin and 2,17-bidecarboxy-2,3-dehydrobetanidin, indicates their generation through two reaction routes with two different quinonoid intermediates: dopachrome derivative and quinone methide. Both lead to the decarboxylative dehydrogenation of betanidin. Subsequent oxidation and rearrangement of the conjugated chromophoric system results in formation of 14,15-dehydrogenated derivatives.
authors.affiliation: Department of Analytical Chemistry, Institute C-1, Faculty of Chemical Engineering and Technology, Cracow University of Technology, ul Warszawska 24, Cracow 31-155, Poland. swybran@chemia.pk.edu.pl
authors.forename: Sławomir
authors.initials: S
authors.lastname: Wybraniec
authors.forename: Paweł
authors.initials: P
authors.lastname: Stalica
authors.forename: Aneta
authors.initials: A
authors.lastname: Spórna
authors.forename: Boris
authors.initials: B
authors.lastname: Nemzer
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Pietrzkowski
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Michałowski
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D050858:Betalains / Q000737:chemistry*; D004563:Electrochemistry; D010084:Oxidation-Reduction; D013053:Spectrophotometry; D053719:Tandem Mass Spectrometry
chemical_list: D000975:Antioxidants; D050858:Betalains