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The search for new antioxidants of natural origin derived from plants and seaweeds is still very important at present. In our study, the acetone extract of A. nodosum was investigated for its potential use as a natural antioxidant, natural feed additive with antibacterial activity and as a tyrosinase inhibitor. This study could be useful in the context of improved utilization of the A. nodosum extract in the food and cosmetics industry, being not only economically advantageous but also environmentally friendly. Extracts showed antioxidant activity with application of different methodologies: 1,1-diphenyl-2-picrilhydracil DPPH· radicals scavenging (39 %, 4 mg of freeze-dried sample), β-carotene-linoleic acid antioxidant assay (11 %, 4 mg of freeze-dried sample), O2· radicals scavenging activity (IC50 0.43 mg mL−1), OH· radicals scavenging activity (IC50 1.55 mg mL−1), and iron chelation ability (IC50 0.56 mg mL−1). The extract showed considerable antibacterial activity being more effective against gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus) than against gram-negative bacteria (Escherichia coli, Enterococcus aerogenes). Results of tyrosinase assay for the acetone extract of Ascophyllum nodosum presented 65.6 % inhibition of tyrosinase activity at the IC50 value of 0.1 mg mL−1. The outcomes of our study support potential utilization of this brown seaweed as a source of natural antioxidants. Antioxidant activity of the studied seaweed can be apparently explained by the free radicals scavenging activity, particularly related to the mechanisms of O 2 − · radicals scavenging activity, OH· radicals inactivation, and iron chelation ability.