Chemical composition and antioxidant potential of Pyropia spiralis and Sargassum natans through a biorefinery-based extraction

Macroalgae are rich in carbohydrates, proteins, essential fatty acids, dietary fibers, and antioxidant compounds, making them valuable sources of functional ingredients and high-value-added products. To improve the extraction and recovery of these metabolites, this study evaluated a sequential biorefinery-based extraction protocol applied to two macroalgal species, the red alga Pyropia spiralis and the brown alga Sargassum natans . The dried and ground algal biomass was cascade extracted using solid-liquid maceration with chloroform:methanol (2:1 v/v), water, water and alkaline hydrolysis, and pressurized water. The extracts were analyzed for lipids, proteins, carbohydrates, and phenolic compounds as chemical composition, and antioxidant potential using ABTS and FRAP assays. Hydrolyzed extracts yielded the highest metabolite recovery, followed by water, pressurized water, and chloroform:methanol extracts. Lipid, carbohydrate, and phenolic contents were recovered within expected ranges for both species. Notably, pressurized extracts of S. natans exhibited the strongest antioxidant capacity. The results underscore the importance of using cascade extraction with diverse solvents to effectively access different target metabolites. The presence of bioactive compounds and antioxidant capacity supports the potential of P. spiralis and S. natans for applications in the nutraceutical, pharmaceutical, and cosmeceutical industries, reinforcing their value in sustainable bioproduct development.