Rising awareness about the advantages of natural antioxidants has driven efforts to explore alternative natural sources for these compounds. Macroalgae are a promising source of these bioactive compounds. Brown macroalgae are renowned for their ecological significance, metabolite diversity, and potent bioactive attributes. These metabolites, spanning polysaccharides, phenolic compounds, and terpenoids, play a dual role by influencing the ecological dynamics of the algae and exhibiting noteworthy bioactive characteristics, highlighting their antioxidant potential as the common driver of their effects. This study aimed to characterize four brown macroalgae by comparing two orders, Fucales (Fucus vesiculosus and Pelvetia canaliculata) and Laminariales (Laminaria ochroleuca and Saccharina latissima), searching for bioactive compounds, namely, pigments and phlorotannins, with antioxidant properties, and to later optimize their extraction by Heat-Assisted Extraction (HAE) and Pressurized Liquid Extraction (PLE). The experiments were designed following a response surface methodology (RSM). Extraction was performed according to the following independent variables: for HAE, time (t, 5-60 min), temperature (T, 30-90°C) and solvent concentration (S, 0-100% ethanol) and for PLE, time (t, 1-50 min), temperature (T, 50-200°C) and ethanol percentage of the solvent (S, 0-100%). Phenolic compounds and pigments were identified by HPLC-ESI-QqQ-MS/MS following the previous methodology. In both cases, PLE improved the extraction of active compounds. The extraction yield of F. vesiculosus – PLE ranged from 9.1 to 63.4%, obtaining the best ratio among the tested species. Phlorotannins and carotenoids were the most frequent compounds to exhibit antioxidant properties. The presence of quinic acid and scopoletin was also characterized. This work will shed light on the optimization and potential of these algae-derived compounds, paving the way for further research in natural antioxidants for industrial application.