Exploration of structure-antifouling relationships of capsaicin-like compounds that inhibit zebra mussel (Dreissena polymorpha) macrofouling.

Macrofouling of aquatic man-made structures by zebra mussels ( Dreissena polymorpha) poses significant economic burdens on commercial freshwater shipping and facilities utilising raw water. The negative environmental impact of some current antifouling technologies has limited their use and prompted investigation of non-organometallic and non-oxidising antifoulants as possible environment-friendly alternatives. The plant-derived natural product capsaicin and 18 other compounds with one or more capsaicin-like structural features were tested for their potential to inhibit zebra mussel byssal attachment at a single high concentration of 30 mu M. Of these, three compounds displaying the highest levels of attachment inhibition where selected for further concentration-response testing. This testing revealed that capsaicin (8- methyl-N-vanillyltrans- 6-nonenamide), N-vanillylnonanamide, and N-benzoylmonoethanolamine benzoate all inhibited byssal attachment with potency values (EC50) in the micromolar range. None of these compounds were lethal to adult specimens of the water flea, Daphnia magna, at concentrations that inhibited mussel byssal attachment.