Biochemical composition, nutritional value, and antioxidant properties of seven seaweed species from the Madeira Archipelago

Biochemical composition and antioxidant activity were assessed in seven seaweeds from Madeira Archipelago, namely, the chlorophyte (Ulva lactuca), the rhodophytes (Asparagopsis taxiformis, Chondrus crispus, Galaxaura rugosa, Grateloupia lanceola and Nemalion elminthoides), and the phaeophyte (Zonaria tournefortii). Seaweed mineral content varied from 16.60 to 84.16 g (100 g)(-1) dry weight (dw). Organic matter, composed by fiber and matrix polysaccharides (8.33 to 54.04 g (100 g)(-1) dw), starch (1.95 to 25.41 g (100 g)(-1) dw), protein (2.80 to 17.55 g (100 g)(-1) dw), and fat (1.46 to 12.04 g (100 g)(-1) dw), was also determined. Asparagopsis taxiformis was found to have substantial quantities of protein, fat, fiber, and matricial polysaccharides, compared to the other analyzed seaweeds. Analysis of antioxidant components included the measurement of chlorophyll a (28.81 to 244.3 g (100 g)(-1) dw), total carotenoids (0 to 297.8 g (100 g)(-1) dw), total phenolic compounds (0 to 2154 mg GAE (100 g)(-1) dw), and total flavonols (7.27 to 604.8 mg QE (100 g)(-1) dw). Zonaria tournefortii was found to possess the highest contents of chlorophyll a, total carotenoids, total phenolic content (TPC), and antioxidant activity, determined through ferric reduction antioxidant potential (FRAP), ferrous ion chelating (FIC), free radical-scavenging assay (FRSA), and beta-carotene bleaching (beta-CB). Statistical analysis showed 38 significant correlations between various biochemical and antioxidant parameters or activity and determined that fat content showed the highest number of correlations. Overall, this study gives a better understanding of Madeira autochthonous seaweeds in their potential of being introduced as a raw material for nutrient supplementation in various food products or to produce functional foods using seaweed natural properties.