title: Application of Electrochemiluminescence for the Evaluation of the Antioxidant Capacity of Some Phenolic Compounds Against Superoxide Anion Radicals.
abstract: This paper for the first time reports on novel and non-enzymatic method for studying the free radical-scavenging properties of phenolic compounds against superoxide anion radicals (O2·(-)) by using the cathodic electrochemiluminescence (ECL) of lucigenin (Luc(2+)). The ECL of Luc(2+) at a glassy carbon (GC) electrode is observed in an aeration electrolytic solution (pH 7), which is believed to be due to the reaction of a one-electron reduced form of Luc(2+) (i.e. a radical cation, Luc·(+)) with in situ electrogenerated O2·(-). The ECL intensity is dependent on the concentration of dissolved oxygen, and is suppressed dramatically by superoxide dismutase (SOD), a typical O2·(-) scavenger. Since the coexisting hydrogen peroxide (H2O2) has no influence on the cathodic ECL of Luc(2+), it is thus suggested that the ECL signal specifically reflected the O2·(-) concentration level generated at the electrode surface. When phenolic compounds were added into the solution, this resulted in the inhibition of ECL signals due to the elimination of O2·(-). The ECL inhibition rate measured at each concentration was compared against the SOD equivalent (U mL(-1)), and the relative antioxidant efficiency, Kao (U mmol(-1) equivalent SOD), was used to evaluate the antioxidant activity of some phenolic compounds, including flavonoids, in this study. Structurally different water-soluble phenols were compared, and those compounds containing to catechol skeletal structure are found to present the higher antioxidant capacity.
authors.affiliation: Department of Chemistry, Faculty of Science, Shinshu University.
authors.forename: Masanori
authors.initials: M
authors.lastname: Matsuoka
authors.forename: Jiye
authors.initials: J
authors.lastname: Jin
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D008163:Luminescent Measurements / Q000379:methods*; D010636:Phenols / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010636:Phenols; D013481:Superoxides; D002244:Carbon