Green Extraction Methods Applied to the Brown Macroalga Saccharina latissima: Assessing Yield, Total Phenolics, Phlorotannins and Antioxidant Capacity

The brown seaweed Saccharina latissima is an abundant, although yet underutilized, source of natural bioactive compounds commonly found in western regions. In recent years, brown algae have garnered attention as promising sources of polyphenols, particularly phlorotannins. The recovery of these relevant components by eco-friendly and energy-efficient methods with solvents GRAS (Generally recognized as safe) contributes to minimizing environmental impact, and promotes sustainability. Pressurized liquid extraction (PLE) and microwave-assisted extraction (MAE) optimized by Box–Behnken design (BBD) were explored for this purpose. The methods were evaluated considering the process yield and the quality of the recovered extracts by phenolic and phlorotannin levels, and their antioxidant capacity was assessed by DPPH and ABTS assays. The optimized MAE techniques (80 °C, 2% EtOH/Water at 40 mL g⁻¹) and PLE2 (80 °C with water) showed the highest extract yields, with increases of 65.76% and 37.36%, respectively, compared to CRE. PLE2 also achieved higher TPC and antioxidant capacity (ABTS) values by 61.88% and 80.39%, respectively. MAE (optimized) increased TPC and ABTS by 53.90% and 36.42%, respectively. Regression analysis of MAE confirmed the accuracy of the models in assessing interaction parameters (adjustment p < 0.05 and adequacy R² > 0.86). Therefore, the study presents eco-efficient approaches for recovering phenolic compounds and antioxidants from brown algae, contributing to the valorization of these resources in the industry and enhancing their application.