pH-Dependent Extraction of Antioxidant Peptides from Red Seaweed <i>Palmaria palmata</i>: A Sequential Approach

Abstract

This study employed a diverse approach to extract antioxidant peptides from red seaweed Palmaria palmata, recognized for its comparatively high protein content. Initially, an aqueous extraction of the entire seaweed was performed, followed by enzymatic hydrolysis of the solid residues prepared from the first step. The effects of three different pH levels (3, 6, and 9) during the aqueous extraction were also examined. Results indicated that the solid fraction from the sequential extraction process contained significantly higher levels of proteins and amino acids than other fractions (p 50 ranging from 2.29 to 8.15 mg.mL−1) demonstrated significantly greater free radical scavengers than the liquid fractions (IC50 ranging from 9.03 to 10.41 mg.mL−1 or not obtained at the highest concentration tested) at both stages of extraction (p 50 = 0.63 ± 0.04 mg.mL−1) and pH 6 (IC50 = 0.89 ± 0.07 mg.mL−1), which were significantly more effective than those from the initial extraction stage (p −1 at pH 3 and 2.43 ± 0.22 vs. 2.51 ± 0.00 mg.mL−1 at pH 6) (p > 0.05), the observed antioxidant properties may be attributed to bioactive amino acids such as histidine, glutamic acid, aspartic acid, tyrosine, and methionine, either as free amino acids or within proteins and peptides.

Keywords

• <i>Palmaria palmata</i>
• aqueous extraction
• enzymatic hydrolysis
• protein
• antioxidant activity
• rhodophyceae