Exploring the bioactive properties of Tetraselmis sp. against the emerging contaminant BDE-47

Tetraselmis sp., a marine microalga widely applied in aquaculture and food biotechnology, is a promising source of bioactive compounds with strong antioxidant properties. These functional molecules plays a key role in mitigating oxidative stress, which may be triggered by environmental stressors such as persistent organic pollutants. This study investigated how the growth phase-dependent variability of Tetraselmis sp. influences its biochemical composition and antioxidant potential, using an integrated biochemical and cell-based approach, emphasizing on its bioactivity against the 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) –induced oxidative stress in Sparus aurata fibroblast cells (SAF-1). Biomass harvested during Growth (GP) and Maturation/Decline phases (MDP) was analyzed for amino acids, fatty acids, pigments, polyphenols, flavonoids, and anthocyanins. Ethanolic extracts were tested for antioxidant capacity (DPPH (2,2-diphényl-1-picrylhydrazyl) and reducing power assays) and cytoprotective effects in vitro. Extracts from the GP exhibited higher antioxidant activity (Inhibition concentration (IC50) = 1.46 mg/mL; effective concentration (EC50) = 5.58 mg/mL), correlating with elevated phenolic and flavonoid contents. Co-exposure of SAF-1 cells with 0.01 μg/mL of these extracts significantly improved cell viability under BDE-47-induced stress conditions at 100 μmol/L. Principal component analysis revealed distinct, growth phase–specific metabolite profiles associated with functional antioxidant responses, highlighting a phase-dependent bioactivity. Overall, this study highlights the relationship between growth phase-dependent metabolic profiles and functional antioxidant and cytoprotective activities of Tetraselmis sp., supporting its potential valorization as a sustainable source of bioactive ingredients for functional food and nutraceutical applications, while emphasizing the relevance of culture phase optimization rather than culture phase equivalence in environmental health–related strategies.