Evaluation of antioxidant and antidiabetic potential of protein from Sargassum ilicifolium extracted via conventional and enzymatic approach

Background & Problem: Diabetes and oxidative stress-related diseases are escalating global health concerns, driving the need for safe, natural alternatives to synthetic drugs which often have adverse side effects. However, conventional protein extraction methods from seaweed often suffer from low efficiency, high energy consumption, or degradation of heat-labile bioactive compounds. Objective: Therefore, this study aimed to extract and characterize protein from Sargassum ilicifolium by comparing conventional (aqueous and alkaline) extraction with enzymatic methods using five specific enzymes: Alcalase, Termamyl, Viscozyme, Celluclast, and AMG. Furthermore, the study sought to evaluate their antioxidant and antidiabetic properties to identify the most effective extraction protocol. Methods: Protein was extracted using aqueous, alkaline, and five enzymatic treatments. To optimize recovery, the extracts were precipitated at two distinct ethanol concentrations: 30% and 70%. Antioxidant activity was evaluated using DPPH, ABTS, and metal chelation assays. Antidiabetic potential was assessed through α-amylase and α-glucosidase inhibition assays. Key Results: Comparative analysis revealed that alkaline extraction yielded the highest total protein content (14.7%), but enzymatic extraction with Termamyl (30% alcohol precipitation) achieved a significant protein yield of 7.3%. Notably, enzyme-assisted extraction showed higher overall efficiency (18.4% for Alcalase) compared to conventional methods, highlighting its sustainability and selectivity. Regarding bioactivity, Termamyl (70% alcohol) exhibited the highest DPPH radical scavenging (44.32 μg Trolox/ml) and metal chelation (74.78 μg EDTA/ml). Viscozyme (70% alcohol) showed the strongest ABTS inhibition (199.57 μg Trolox/ml). In terms of antidiabetic potential, Termamyl (30% alcohol) demonstrated the highest α-glucosidase inhibition (IC₅₀ = 4.15 μg/ml), while Termamyl (70% alcohol) showed 75.93% α-amylase inhibition. Significance & Novelty: Unlike previous studies that focused on single enzymes or methods, this study provides a comprehensive comparison of multiple enzyme types (proteases vs. carbohydrases) on S. ilicifolium. This study demonstrates that enzymatic extraction is a promising, sustainable alternative for producing bioactive peptides with dual antioxidant and antidiabetic properties. These findings offer valuable insights for the development of nutraceuticals, functional foods, and aquaculture feeds, addressing the challenge of finding efficient, eco-friendly ways to harness marine bioactive compounds.