Bioassay-guided discovery of antifouling nucleosides from the cyanobacterium Leptothoe sp. LEGE 181152: Efficacy, molecular targets, and ecotoxicological assessment

Abstract

The prevention of marine biofouling remains a global challenge due to environmental concerns associated with current biocidal antifouling (AF) agents and increasing regulatory pressure to ban such biocides. Natural products present promising alternatives as effective and eco-friendly AF solutions, with cyanobacteria emerging as a rich source of bioactive compounds due to their remarkable biosynthetic potential. In this study, the AF bio-guided discovery of natural products from the cyanobacterium Leptothoe sp. LEGE 181152 led to the isolation of two nucleosides - adenosine (1) and 2'-deoxyadenosine (2), which were for the first time explored as innovative AF agents. A comprehensive approach was undertaken, including AF efficacy across biological levels, ecotoxicity and ecological risk assessment, and molecular targets elucidation. Compounds 1 and 2 successfully inhibited mussel settlement (EC₅₀ = 6.63; 8.74 µM), without exhibiting lethal effects (LC₅₀ > 200 µM). At these concentrations, both compounds increased the in vitro acetylcholinesterase activity. Functional enrichment analysis revealed effects on proteins associated to ciliary motility and ATP metabolism. Additionally, both compounds inhibited the growth of Navicula sp. ( ̴40 % for 1, and 60 % for 2). In addition to showing no effect on marine biofilm-forming marine bacteria, ecotoxicological assays with nauplii of Artemia salina and Amphibalanus amphitrite revealed no acute toxicity in these species. Furthermore, simulated environmental data indicated a low potential for bioaccumulation and low environmental persistence. Overall, these findings identify adenosine and 2'-deoxyadenosine as novel, low-risk natural AF agents, with real-world applicability as promising candidates for incorporation into marine coatings, thereby contributing to the development of more sustainable solutions for biofouling management.

Keywords: 2’-Deoxyadenosine; Adenosine; Cyanobacteria; Natural antifouling alternatives; Nucleosides.