Abstract: Polymeric alkylpyridinium salts (poly-APS) isolated from the Mediterranean marine sponge, Haliclona (Rhizoniera) sarai, effectively inhibit barnacle larva settlement and natural marine biofilm formation through a non-toxic and reversible mechanism. Potential use of poly-APS-like compounds as antifouling agents led to the chemical synthesis of monomeric and oligomeric 3-alkylpyridinium analogues. However, these are less efficient in settlement assays and have greater toxicity than the natural polymers. Recently, a new chemical synthesis method enabled the production of poly-APS analogues with antibacterial, antifungal and anti-acetylcholinesterase activities. The present study examines the antifouling properties and toxicity of six of these synthetic poly-APS using the barnacle (Amphibalanus amphitrite) as a model (cyprids and II stage nauplii larvae) in settlement, acute and sub-acute toxicity assays. Two compounds, APS8 and APS12-3, show antifouling effects very similar to natural poly-APS, with an anti-settlement effective concentration that inhibits 50% of the cyprid population settlement (EC50) after 24 h of 0.32 mg/L and 0.89 mg/L, respectively. The toxicity of APS8 is negligible, while APS12-3 is three-fold more toxic (24-h LC50: nauplii, 11.60 mg/L; cyprids, 61.13 mg/L) than natural poly-APS. This toxicity of APS12-3 towards nauplii is, however, 60-fold and 1200-fold lower than that of the common co-biocides, Zn- and Cu-pyrithione, respectively. Additionally, exposure to APS12-3 for 24 and 48 h inhibits the naupliar swimming ability with respective IC50 of 4.83 and 1.86 mg/L.
Keywords: Amphibalanus amphitrite; antifouling; natural product antifoulants; alkylpyridinium polymers; Haliclona (Rhizoniera) sarai; barnacle; settlement assay; toxicity assay; swimming inhibition assay
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Piazza, V.; Dragić, I.; Sepčić, K.; Faimali, M.; Garaventa, F.; Turk, T.; Berne, S. Antifouling Activity of Synthetic Alkylpyridinium Polymers Using the Barnacle Model. Mar. Drugs 2014, 12, 1959-1976.
Piazza V, Dragić I, Sepčić K, Faimali M, Garaventa F, Turk T, Berne S. Antifouling Activity of Synthetic Alkylpyridinium Polymers Using the Barnacle Model. Marine Drugs. 2014; 12(4):1959-1976.
Piazza, Veronica; Dragić, Ivanka; Sepčić, Kristina; Faimali, Marco; Garaventa, Francesca; Turk, Tom; Berne, Sabina. 2014. "Antifouling Activity of Synthetic Alkylpyridinium Polymers Using the Barnacle Model." Mar. Drugs 12, no. 4: 1959-1976.