Broad spectrum effects of secondary metabolites from the red alga<i>delisea pulchra</i>in antifouling assays

Abstract

In this study the antifouling activity was investigated of a series of chemically related, halogenated furanones&#13;\nisolated from Delisea pulchra (Greville) Montagne, a red alga which is rarely fouled in the field. The&#13;\nmetabolites were tested in laboratory assays against representatives of the three major groups of fouling&#13;\norganisms, the barnacle Baianus amphitrite amphitirite Darwin, the macroalga Ulva lactuca Linnaeus and a&#13;\nmarine bacterium (strain SW 8). Settlement of barnacle cyprid larvae was strongly inhibited, with an EC50 of&#13;\n&lt; 25 ng·mr1 (25 ppb) for some compounds. The settlement and growth of algal gametes was also strongly&#13;\ninhibited, in some cases at concentrations as low as 25 ng·cm-2&#13;\n• Growth of the marine bacterium SW8 was&#13;\ninhibited more strongly than by the common antibiotic gentamicin. Overall, activity of the D. pulchra&#13;\nmetabolites was comparable to that of the heavy metals and biocides currently used in antifouling paints.&#13;\nHowever, no single compound was most active in all tests and some metabolites effective against one organism&#13;\nshowed Iittle or no activity a·gainst the others. The high but variable level of activity of the D. pulchra&#13;\nmetabolites, coupled with their small size, relative stability, and ability tobe synthesized suggest their potential&#13;\nuse as active ingredients in antifouling coatings.