Analytical Sciences

Abstract − Analytical Sciences, 31(7), 629 (2015).

Application of Electrochemiluminescence for the Evaluation of the Antioxidant Capacity of Some Phenolic Compounds Against Superoxide Anion Radicals
Masanori MATSUOKA and Jiye JIN
Department of Chemistry, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan
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 (Luc2+). The ECL of Luc2+ 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 Luc2+ (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 Luc2+, 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.