In vitro and cellular antioxidant activities of seaweed extracts prepared from five brown seaweeds harvested in spring from the west coast of Ireland

The antioxidant potential of methanolic extracts of brown seaweeds was assessed by Total Phenol Content, Ferric Reducing Antioxidant Power (FRAP), β-carotene bleaching and the DPPH scavenging assays. Ascophyllum nodosum, Pelvetia canaliculata, and Fucus serratus contained the highest phenol concentrations while Fucus vesiculosus and F. serratus exhibited the highest FRAP activities. F. vesiculosus and A. nodosum were the most effective extracts at scavenging DPPH radicals and preventing β-carotene bleaching. The antioxidant activity of the seaweed extracts was also evaluated in Caco-2 cells. All extracts significantly (P < 0.05) increased glutathione (GSH) content of cells after 24 h. Caco-2 cells were also pre-treated with seaweed extract for 24 h followed by exposure to hydrogen peroxide (H₂O₂). Antioxidant enzyme activity (catalase (CAT) and superoxide dismutase (SOD)) was assessed and DNA damage was measured using the comet assay. P. canaliculata was the most effective at preventing H₂O₂-mediated SOD depletion in Caco-2 cells while F. serratus exhibited the best DNA protective effects.