A chemical investigation of the marine-derived fungi Aspergillus versicolor led to the isolation of a new aromatic polyketide (1), The structure was elucidated by spectroscopic analysis, and its radical-scavenging activity, reducing power, and inhibitory activity to lipid oxidation were investigated. Those activities of compound 1 were compared with standard antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiarybutylhydroquinone (TBHQ), and ascorbic acid ($V_C$). Compound 1 showed antioxidant activity comparable to that of BHA, and siginificantly higher than that of BHT.