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

► Seaweed extracts reduced hydrogen peroxide-induced cell DNA damage. ► Seaweed extracts reduced H2O2-induced superoxide dismutase depletion. ► Seaweed extracts scavenged DPPH radicals. ► Seaweed extracts exhibited FRAP activities. ► Some seaweed extracts prevented β-carotene bleaching.