Electrochemical Study of Flavonoids in Acetonitrile: Structure-Activity Relationships N. Arroyo-Currás, M. F. Videa Department of Chemistry, Tecnológico de Monterrey, Monterrey, N. L. 64849, Mexico Relations between structure, antioxidant capacity and formal redox potentials (E°’) of six flavonoids dissolved in acetonitrile were studied by cyclic voltammetry and square wave voltammetry using a glassy carbon electrode. This work shows correlation between the electrochemical parameter E°’ and the number of hydroxyl groups present in the B ring of flavonoids. Besides, it has been observed that E°’ measured as a function of B ring oxidation depends considerably on the functional groups present in the ring C of these molecules. Since antioxidant activity of flavonoids is attributed to their proton-donating, the results of this work were compared to previous reports regarding the antioxidant capacity of these compounds. Even though the antioxidant activity of flavonoids depends on several factors, the conclusions of this investigation suggest that the E°’ value should be considered as a key parameter for the evaluation of antioxidant activity. Introduction Flavonoids are a group of polyphenolic compounds ubiquitously found in the plant kingdom, with over 8,000 molecules known to date (1). Their basic structure is the flavan nucleus, which is shown in Figure 1. It essentially consists of 15 carbon atoms arranged in three rings (C 6 -C 3 -C 6 ), labeled as A, B, or C respectively (2). The great number of different flavonoid compounds is organized in classes that differ between them in the level of oxidation and pattern of substitution of the C ring. Moreover, individual differences within a class result from the variation in number and arrangement of the hydroxyl groups present in the A and B rings. Figure 1. Flavonoids basic skeleton Among the various classes of flavonoids, those important for the purposes of this investigation are flavonols, anthocyanidins and flavanols (see Table I). These three classes of flavonoids are not only the most frequently found in nature, but also can be found in considerable amounts within several fruits and flowers (3,4). They are part of ECS Transactions, 29 (1) 349-359 (2010) 10.1149/1.3532331 ©The Electrochemical Society 349 Downloaded 21 Mar 2012 to 198.213.206.70. Redistribution subject to ECS license or copyright; see http://www.ecsdl.org/terms_use.jsp