Potential antioxidative activities of enzymatic extracts from seven species of brown seaweeds were evaluated using four different reactive oxygen species (ROS) scavenging assays containing DPPH (1,1-diphenyl-2-pricrylhydrazyl) free radical, superoxide anion, hydroxyl radical and hydrogen peroxide scavenging assay. The brown seaweeds were enzymatically hydrolyzed to prepare water-soluble extracts by using five carbohydrate degrading enzymes (Viscozyme, Celluclast, AMG, Termamyl and Ultraflo) and five proteases (Protamex, Kojizyme, Neutrase, Flavourzyme and Alcalase) of commercial and inexpensive enzymes obtained from Novozyme Co. (Novozyme Nordisk, Bagsvaerd, Denmark). The enzymatic extracts exhibited more prominent effects in hydrogen peroxide scavenging activity (approximately 90%) compared to the other scavenging activities and the activity of enzymatic extracts was even higher than that of the commercial antioxidants. In particular, Ultrafto and Alcalase extracts of S. horneri were dose-dependent and thermally stable. Moreover the two enzymatic extracts strongly inhibited DNA damage (approximately 50%). Those extracts showed significantly (p < 0.05) remarkable scavenging effects in DPPH free radical scavenging assay and the activity indicated a marked correlation with phenolic contents. From the results, enzymatic extracts of the brown seaweeds might be valuable antioxidative sources. (c) 2005 Elsevier Ltd. All rights reserved.