Ecotoxicological hazard assessment of nature-inspired synthetic compounds for antifouling applications.

The accumulation of microorganisms and macroorganisms on aquatic surfaces poses economic and ecological challenges, particularly in maritime transport. Traditional antifouling methods, such as biocidal coatings containing toxic compounds like tributyltin (TBT) and copper, are effective but harmful to the environment. This study investigates the ecotoxicological hazards of two nature-inspired compounds (NIAFs), previously investigated for antifouling applications: the polyphenol GBA and the dihydrochalcone DH345, derived from polyphenols and flavonoids, respectively. The ecotoxicity of these compounds was evaluated using standardized assays with various species, including embryos of Danio rerio (zebrafish) (OECD TG 236), the algae Raphidocelis subcapitata (OECD TG 201), and the bacteria Aliivibrio fischeri (ISO 11348-2), along with nuclear receptor transactivation assays in Mytilus galloprovincialis (Mediterranean mussel). Gallic acid derivative GBA and 24h-transformation products showed low toxicity in zebrafish embryos, while dihydrochalcone DH345 inflicted developmental toxicity in zebrafish at 1 mg/L and above. Comparatively, tralopyril, a commercial biocide, exhibited significant toxicity at lower concentrations. Transcriptomic analysis of zebrafish embryos treated with GBA revealed selective gene modulation related to stress response, ion transport, and protein synthesis. Both GBA and DH345 were shown to inhibit algae growth at 0.1 mg/L. Aliivibrio fischeri assay showed no toxic effects for any of the tested compounds. Nuclear receptor transactivation assays conducted with GBA revealed no activation of PPAR (Peroxisome Proliferator-Activated Receptor) or PXR (Pregnane X Receptor) receptors. These findings suggest that GBA and DH345 may represent potential antifouling candidates with lower toxicity than tralopyril, under the tested conditions. However, further research is needed to evaluate their potential long-term ecological impacts, particularly chronic toxicity across various organisms, and environmental risk. This study advances the pursuit of sustainable antifouling solutions that prioritize environmental protection.