Influence of pressurised liquid extraction and solid–liquid extraction methods on the phenolic content and antioxidant activities of <scp>I</scp>rish macroalgae

<jats:title>Summary</jats:title><jats:p>The efficiencies of pressurised liquid extraction (<jats:styled-content style="fixed-case">PLE</jats:styled-content>) and a traditional solid–liquid extraction (<jats:styled-content style="fixed-case">SLE</jats:styled-content>) at extracting antioxidant polyphenols from <jats:styled-content style="fixed-case">I</jats:styled-content>rish macroalgae <jats:italic><jats:styled-content style="fixed-case">A</jats:styled-content>scophyllum nodosum</jats:italic>,<jats:italic> <jats:styled-content style="fixed-case">P</jats:styled-content>elvetia canaliculata</jats:italic>,<jats:italic> <jats:styled-content style="fixed-case">F</jats:styled-content>ucus spiralis</jats:italic> and <jats:italic><jats:styled-content style="fixed-case">U</jats:styled-content>lva intestinalis</jats:italic> were compared. <jats:styled-content style="fixed-case">PLE</jats:styled-content> was more effective for extracting polyphenols with acetone/water (80:20); however, when food‐friendly solvents of ethanol/water (80:20) and water were employed, <jats:styled-content style="fixed-case">SLE</jats:styled-content> resulted in higher phenolic content in brown macroalgal extracts. For example, the <jats:italic><jats:styled-content style="fixed-case">F</jats:styled-content>ucus spiralis </jats:italic><jats:styled-content style="fixed-case">SLE</jats:styled-content> water and ethanol/water extracts displayed total phenolic contents (<jats:styled-content style="fixed-case">TPC</jats:styled-content>s) of 130.58 ± 2.78 and 142.81 ± 1.77 μg phloroglucinol equivalents (<jats:styled-content style="fixed-case">PGE</jats:styled-content>) mg<jats:sup>−1</jats:sup> sample, respectively, compared with <jats:styled-content style="fixed-case">TPC</jats:styled-content>s of 90.79 ± 1.16 and 124 ± 6.54 μg <jats:styled-content style="fixed-case">PGE</jats:styled-content> mg<jats:sup>−1</jats:sup> sample for the corresponding <jats:styled-content style="fixed-case">PLE</jats:styled-content> extracts. All <jats:styled-content style="fixed-case">SLE</jats:styled-content> aqueous ethanolic macroalgal extracts possessed higher <jats:styled-content style="fixed-case">DPPH</jats:styled-content> radical scavenging abilities (<jats:styled-content style="fixed-case">RSA</jats:styled-content>) and ferric reducing antioxidant power (<jats:styled-content style="fixed-case">FRAP</jats:styled-content>) than their <jats:styled-content style="fixed-case">PLE</jats:styled-content> equivalents<jats:bold>.</jats:bold> This study indicates that the application of high extraction temperatures (50–200 °C) and pressures (500–3000 psi) used in <jats:styled-content style="fixed-case">PLE</jats:styled-content> does not enhance the antioxidant activities of macroalgal extracts relative to <jats:styled-content style="fixed-case">SLE</jats:styled-content> extraction. The ability to produce antioxidant food‐friendly macroalgal extracts using <jats:styled-content style="fixed-case">SLE</jats:styled-content> could represent significant cost reductions on an industrial scale further enhancing the potential of macroalgal polyphenols to be used in functional food preparations.</jats:p>