Phytochemistry diversity and antioxidant activities of Cladostephus spongiosus (Hudson) C. Agardh

Cladostephus spongiosus (Hudson) C. Agardh is a cosmopolitan brown alga, yet its phytochemical profile and biological potential remain scarcely investigated. This study provides the first comprehensive assessment of C. spongiosus collected from the Moroccan Strait of Gibraltar (Fardioua coastline). Five extracts were evaluated for total phenolic, flavonoid, and tannin contents, and chemically characterized for bioactive compounds, and assessed for antioxidant properties. Nine compounds were identified, several reported here for the first time in C. spongiosus. Among the extracts the ethanolic and the dichloromethane extracts displayed the highest total phenolic and flavonoid contents, with the dichloromethane also exhibiting the strongest ABTS radical scavenging activity (318.07 ± 5.3 mg/TE g dry extract). The methanol extract demonstrated the strongest anti-DPPH potential. The aqueous extract contained the highest tannin content and showed the greatest metal chelating capacity, as well as the strongest reducing power in the FRAP assay (31.37 ± 0.20 mg/TE g dry extract). The hexane extract displayed notable reducing power activity in the CUPRAC assay and was the most potent in terms of total antioxidant capacity. Overall, our findings highlight C. spongiosus as promising source of antioxidants and bioactive compounds, underscoring its nutraceutical potential.