Antifouling activity of sponge-derived polybrominated diphenyl ethers and synthetic analogues

Abstract

The antifouling (AF) activity of 2-hydroxy-4-(3-hydroxy-5-methylphenoxy)- 6-methylbenozoic acid methyl ester (1), 3,5-dibromo-2-(2′,4′-dibromophenoxy)phenol (2); 3,4,5-tribromo-2-(2′,4′-dibromophenoxy)phenol (3), 3,4,5-tribromo-2-(2′-bromophenoxy)phenol (4), 3,5-dibromo-2(2′,4′-dibromophenoxy)phenol (5), 3,4,5,6-tetrabromo-2-(2′-bromophenoxy)phenol (6); 4-phenoxyphenol (7), 4-phenoxyaniline (9), 1-chloro-4-phenoxybenzene (10); 1-bromo-4-phenoxybenzene (13) was investigated against marine bacteria, a diatom, barnacle larvae and mussel juveniles. The naturally occurring compound 2 showed the strongest AF activity in all bioassays but lacked toxicity. It inhibited the growth of all tested bacterial strains (MIC = 0.02 – 1.52 μM) and its 50% effective concentrations (EC₅₀) were 0.24 μM (diatom test), 0.66 μM (mussel test) and 1.26 μM (barnacle test). Among the commercially available derivates, compound 7 was the most active in bacterial and diatom bioassays but its activity was lower than that of compound 2. Overall, the naturally occurring compounds showed stronger activity than the commercially available analogues and could be possible future non-toxic AF candidates.

Keywords:

• antifouling compounds
• diphenyl ethers
• marine diatoms
• marine bacteria
• marine sponges
• Mytilus edulis

Acknowledgements

Studies of SD were supported by an Alexander von Humboldt Fellowship. PP wishes to thank BMBF (cluster of excellence BIOTECMarin) for their support and SD thanks Mrs Y. Plakhotnikova for her help with the bacterial bioassays. The authors acknowledge the comments of three anonymous reviewers that significantly improved this manuscript.