Antioxidant activities of Sargassum horneri solvent fractions against urban particulate matter-induced oxidation

Urban particulate matter (PM) significantly contributes to air pollution. Sargassum horneri was extracted using ethanol (SHE) and subsequently partitioned with n-hexane, chloroform, ethyl acetate, and water. Antioxidant activities of fractions, including DPPH and ABTS⁺ radical, hydrogen peroxide, hydroxyl radical scavenging activities, and metal chelating effects, were evaluated against oxidative damage induced by PM. Through fractionation of SHE, total phenolic and total flavonoid contents were increased from 17.53 to 31.91 mg GAE/g and 58.61 to 320.60 mg QE/g. The chloroform, ethyl acetate, and n-hexane fractions significantly enhanced antioxidant activities. Notably, the metal chelating effects of n-hexane, chloroform, and ethyl acetate fractions were substantial (93.29, 106.50, and 94.18%). PM-induced oxidation resulted in a decrease in antioxidant activity, with the chelating effect being most markedly reduced due to the presence of transitional metals. These results suggest that S. horneri can be utilized as a natural antioxidant, effectively mitigating oxidative damage by PM.