Contribution of in vitro simulated gastrointestinal digestion to the antioxidant activity of Porphyra dioica conchocelis

Porphyra dioica is an Atlantic red seaweed species with economic potential. While its blades are of significant interest in food, feed and cosmetic sectors, little is known about the potential value of conchocelis, the microscopic filamentous sporophytes corresponding to the Porphyra early life stage. The aim of this study was to characterise, for the first time, the proteinaceous fraction of Porphyra dioica conchocelis, evaluating the contribution of in vitro simulated gastrointestinal digestion to their antioxidant activity. Conchocelis produced under controlled growth conditions were submitted to simulated gastrointestinal digestion. The digested samples were characterized for their protein/peptide and free amino acid profile. The digestates were further assessed for their antioxidant properties using different in vitro methods: 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azinobis-(3-ethyl-benzothiazoline-6-sulfonate) and hypochlorous acid scavenging assays, ferric reducing antioxidant power activity and oxygen radical absorbance capacity assay. The results showed that conchocelis had a protein content of 26% (dry weight). The in vitro simulated gastrointestinal digestion promoted the generation of peptides and the release of essential (Lys > Leu > Phe) and non-essential amino acids (Arg > Glu). Overall, simulated gastrointestinal digestion treatment improved the antioxidant activity of the algal biomass. The results demonstrate the potential of conchocelis as a source of dietary protein and essential amino acids, providing new inputs to generate novel conchocelis-derived hydrolysates/peptides with enhanced antioxidant properties, ultimately of potential value as functional food or cosmetic ingredients.