Are Algae a Good Source of Antioxidants? Mechanistic Insights into Antiradical Activity of Eckol

Eckol (<b>Eck</b>), a polyphenolic compound of marine origin, exhibits strong scavenging activity against hydroperoxyl radicals. This study explores its acid-base speciation in aqueous media and evaluates its antioxidant potential through electronic, thermochemical, and kinetic analyses under biologically relevant conditions. The deprotonated species of <b>Eck</b> display exceptionally high rate constants for hydrogen atom transfer, indicating a potent antiradical mechanism. The apparent rate constant, accounting for species distribution at physiological pH and the molar fraction of ^•OOH, was calculated as 1.09 × 10⁷ M^-1·s^-1. Compared to related compounds, <b>Eck</b> demonstrates outstanding hydroperoxyl radical-scavenging capacity, supporting its potential as a natural antioxidant in biological systems.