Red Macroalgae as Sources of Antioxidant and Multifunctional Ingredients for Functional Foods: A Biorefinery Approach

Given the established interplay between oxidative stress, cholinergic dysfunction, and metabolic imbalance in cognitive decline, this study investigated the multifunctional potential of three red macroalgae from the Madeira Archipelago (Asparagopsis taxiformis, Grateloupia lanceola, and Nemalion elminthoides) using a sequential biorefinery approach. Marine algae represent a sustainable source of functional food ingredients due to their rich content in bioactive compounds and their compatibility with low-impact production systems. Protein, ethanolic (phenolic-rich), and polysaccharide fractions were obtained through direct extraction and scalable biorefinery processing. Antioxidant activity was evaluated using ORAC, DPPH, FRAP, and FIC assays, while functionality relevant to human health was assessed through acetylcholinesterase, butyrylcholinesterase, and α-glucosidase inhibition. Protein extracts, particularly from N. elminthoides, exhibited strong hydrogen atom transfer-based antioxidant capacity, whereas ethanolic extracts demonstrated multifunctional activity, combining radical scavenging, metal chelation, and enzyme inhibition associated with neuroprotective and glycemic-regulation potential. Polysaccharide fractions contributed mainly to iron chelation and reducing capacity. Correlation analyses highlighted the complementary nature of antioxidant and bioactivity assays. Overall, these findings support the potential of Madeira red macroalgae as functional food ingredients and emphasize the importance of optimized biorefinery strategies to maximize nutritional and health-related benefits.