Mechanisms of Antioxidant Activities of Fullerenols from First-Principles Calculation

Fullerenols possess excellent antioxidant activity, in which they can scavenge all of the major physiologically relevant reactive oxygen species (ROS). However, the underlying ROS-scavenging mechanisms of C₆₀ fullerenols are not completely understood. Using density functional theory calculations, we investigated ^•OH-, O₂ ^•--, and H₂O₂-scavenging mechanisms of C₆₀ fullerenols and the correlations between hydroxyl distributions and radical-scavenging ability. For scavenging ^•OH and O₂ ^•-, H^• donation and electron transfer via hydrogen bonds, respectively, are the dominant mechanisms for C₆₀ fullerenols. Although the obtained fullerenols simultaneously contain radicals and anions, there is an isolated OH anion which possesses the activity of eliminating H₂O₂. The ^•OH-scavenging activity depends on the distribution of hydroxyls according to the calculations for ten C₆₀(OH)₂₄ isomers. Fullerenols, in which the distribution of hydroxyls leads to low redox potential (ϵ) values, possess high scavenging activity. For the nonmagnetic fullerenols, activity relies on the number of sp² substructures, in which the greater their number is, the lower the activity of the fullerenols. The results will be of fundamental importance in understanding the antioxidant activities of fullerenols.