Seaweeds are widely recognized as valuable sources of bioactive secondary metabolites with significant medicinal and industrial potential. The biological properties of the brown seaweed Stypocaulon scoparium crude extract were investigated. An algal sample was collected from the coastal region of Tipaza, Algeria, and the extract was evaluated for total polyphenol and flavonoid contents, and antioxidant, antibacterial, anti-inflammatory, and anticancer activities. The extract is rich in polyphenols and flavonoids, exhibiting strong antioxidant capacity. It showed notable antimicrobial activity was observed against various pathogens, with pronounced strong antifungal efficacy, and significantly reduced MCF7 breast cancer cell viability, indicating anticancer potential. Anti-inflammatory activity was demonstrated by inhibition of protein denaturation, with the extract exhibiting a distinct concentration-dependent effect. In summary, Stypocaulon scoparium was identified as a promising source of bioactive compounds. However, further investigations are required to elucidate their mechanisms of action and to validate their pharmaceutical applications.

Aflatoxins, primarily produced by fungi belonging to Aspergillus section Flavi, are a major concern for food and feed safety. This study evaluated the seaweed Cystoseira compressa and its biosynthesized zinc oxide nanoparticles (ZnONPs) as green agents to inhibit fungal growth and reduce aflatoxin B1 contamination in animal feed. Aspergillus section Flavi isolates were obtained from maize grains and identified by ITS sequencing. The seaweed extract was chemically characterized by HPLC, while the ZnO-NPs were confirmed and analyzed using UV-Vis spectroscopy, FTIR, EDX, DLS, zeta potential, XRD, and SEM. HPLC-FLD analysis revealed significant variability in aflatoxin B1 concentration, ranging from 96.67 to 5501.4 μg/kg. ZnO-NPs displayed stronger antifungal activity than the seaweed extract, inhibiting mycelial growth by up to 75.33%. They also significantly reduced aflatoxin B1 production both in vitro and in situ. In addition, ZnO-NPs caused a concentration-dependent reduction in ergosterol content, reaching 66.4% at 5 mg/mL, suggesting disruption of fungal membrane integrity. These findings highlight the potential of seaweed-mediated ZnO-NPs as an environmentally friendly alternative to conventional antifungal agents for controlling A. flavus growth and reducing aflatoxin contamination in feed.