How Do Phenolic Compounds React toward Superoxide Ion? A Simple Electrochemical Method for Evaluating Antioxidant Capacity

摘要

The reactivities of different phenols and polyphenolsnversus superoxide ion (O2n•-) were investigated as anneasy-to-handle electrochemical method for evaluatingnantioxidant capacities. In view of this application, thenO2/O2n•- couple and associated reactions between O2n•-nand polyphenols (or phenols) were examined in annaprotic solvent [dimethylformamide (DMF)] by cyclicnvoltammetry. Comparisons based on simple criterian(reversibility of the O2 reduction in the presence of thenphenolic compound, electron stoichiometry, or apparentnkinetic constants) allow discriminations betweennthe possible mechanistic pathways (acid-base or radicalnreaction type). The results highlight that the protontransfernand radical-transfer pathways are both presentnfor monophenols and polyphenols, with the relativencontributions of the two pathways depending on thenphenol structure. In agreement with the literature,npolyphenols containing an o-diphenol ring (as in flavonoids)nwere found to present the highest reactivities.