Antioxidant Power of Vitexin and Isovitexin Against OOH Radicals: A Comparative Theoretical Investigation

The antioxidant activity of vitexin and isovitexin─flavonoids widely found in various plants and used in traditional medicine─has been theoretically evaluated against the OOH radical. Multiple reaction mechanisms, including hydrogen atom transfer, single electron transfer, and radical adduct formation, were considered. The study accounts for all species present in aqueous solution at physiological pH as well as in lipid-like environments. Both compounds exhibit similar antioxidant activities, with apparent rate constants of 1.45 × 10³ M^-¹ s^-¹ for vitexin and 4.78 × 10³ M^-¹ s^-¹ for isovitexin. Compared to Trolox, a commonly used reference compound, their radical scavenging capacities are slightly lower.