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

Eckol (Eck), 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 Eck 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, Eck demonstrates outstanding hydroperoxyl radical-scavenging capacity, supporting its potential as a natural antioxidant in biological systems.