Abstract
Marine macroalgae generally keep their surface free from fouling organisms by their antifouling defence. Antifouling activity has been attributed to the production of secondary metabolites. In the present study, antifouling performance of the macroalga Halimeda sp., collected from the Red Sea coastal waters, was assessed using extracts prepared through various methods, including surface extraction, wet sample extraction and dried sample extraction. The solvents methanol and hexane were used to assess the effect of solvents on bioactivity. Results indicated that extracts of the macroalga inhibited growth and settlement of a biofilm-forming bacterial strain. Though the extracts prepared using different methods and solvents showed inhibitory activities, considerable variation was observed between different assays. Hexane extracts showed strong bacterial growth inhibitory activities in the spectrophotometric assay. The extract of dried algal samples also showed strong growth inhibitory activity, while the extract obtained from fresh algal samples exhibited strong antibiofilm activity. GC-MS analysis showed variations in the biochemical profile of the crude extracts prepared by different methods. In conclusion, results of the present study indicated that the potential bioactive metabolites present in the crude extracts of the marine macroalga Halimeda sp. could be used as a natural antibiofilm and as an antifouling compound.