Extraction and Optimization of Fucoidan From <i>Sargassum muticum</i> Using Acidic Eutectic Solvents and Evaluation of Their Effects on Fibroblast Cell Lines

Fucoidan, a sulfated polysaccharide extracted from the cell wall of macroalgae such as S. muticum, exhibits promising biological properties. This study investigated a green extraction using deep eutectic solvents (DESs), with an emphasis on process optimization and bioactive evaluation of fucoidan. The most efficient DES was lactic acid with glycerol (LacAc:Gly) at 60°C, with 4% water and a solid/liquid ratio of 0.1167, resulting in a yield of 6.6%, a sulfate content of 0.170 mg/mg, and a uronic acid content of 0.023 mg/mg. The chemical and structural composition of fucoidan were evaluated by colorimetric methods, FTIR, and NMR. Antioxidant activity was assessed by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate (ABTS, 25.84%), 2-diphenyl-1-pricylhydrazyl (DPPH, 30.45%), and ferric reducing antioxidant power (FRAP, 690 µg/µg) assays. Cellular assays with L929 fibroblasts showed that concentrations of 50 and 75 µg/mL stimulated cell viability, with 179% colony formation and 449 invasive cells, suggesting positive effects on cell proliferation and migration. Therefore, the results indicate that fucoidan extracted with LacAc:Gly has high bioactive potential, demonstrating the viability of green eutectic solvents as a sustainable alternative for the utilization of bioactive compounds from brown algae.