In Vitro and Intracellular Antioxidant Activities of Brown Alga Eisenia bicyclis

The antioxidant activities of a methanolic extract of Eisenia bicyclis and its organic solvent fractions, including dichloromethane ( CH₂Cl₂ ), ethyl acetate (EtOAc), n-butanol (n-BuOH), and water ( H₂O ) fractions, were investigated. Scavenging activities against DPPH, hydroxyl, superoxide anion, and peroxynitrite radicals were evaluated using electron spin resonance spectrometry; intracellular reactive oxygen species (ROS) were evaluated by a 2',7'-dichlorofluorescein diacetate assay using RAW264.7 mouse macrophages. The antioxidant activities of the individual fractions were: EtOAc>n-BuOH> CH₂Cl₂ > H₂O . The EtOAc fraction exhibited strong radical scavenging activity and a significantly reduced ROS level in RAW264.7 cells. Moreover, the phenolic contents of the extract and fractions followed the same order as their radical scavenging activities. Our results indicate that E. bicyclis is a valuable natural source of antioxidants that may be applicable to the functional food industry.