title: Redox behaviour of verbascoside and rosmarinic acid.
abstract: The electrochemical oxidation mechanisms of rosmarinic acid (RA) and verbascoside (VB), both caffeic acid esters with two catechol moieties, were investigated. The redox mechanism is associated with the oxidation of the catechol groups, and was studied over a wide pH range by cyclic, differential pulse and square wave voltammetry, using a glassy carbon electrode. The voltammetric study revealed that both molecules, RA and VB, are reversibly oxidized in two successive pH-dependent steps each with the transfer of two electrons and two protons. Moreover, it was found that the first oxidation step is associated with the caffeic acid moiety, whereas the second oxidation step corresponds to the oxidation in VB of the hydroxytyrosol group and in RA of the 3,4-dihydroxyphenyl lactic acid residue.
authors.affiliation: Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Coimbra, Portugal.
authors.forename: Eric de Souza
authors.initials: Ede S
authors.lastname: Gil
authors.forename: Teodor Adrian
authors.initials: TA
authors.lastname: Enache
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Oliveira-Brett
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002934:Cinnamates / Q000737:chemistry*; D053630:Depsides / Q000737:chemistry*; D055664:Electrochemical Techniques; D004566:Electrodes; D004583:Electrons; D005960:Glucosides / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000737:chemistry; D000097123:Rosmarinic Acid; D059808:Polyphenols
chemical_list: D000975:Antioxidants; D002934:Cinnamates; D053630:Depsides; D005960:Glucosides; D010636:Phenols; D010626:Phenylethyl Alcohol; D000097123:Rosmarinic Acid; C005975:3,4-dihydroxyphenylethanol; C058956:acteoside; D059808:Polyphenols