Screening of biological activities of extracts of Ralfsia verrucosa, Petalonia fascia and Scytosiphon lomentaria (Phaeophyceae, Scytosiphonales) for potential antifouling application

Fouling process is often detrimental to the efficiency of man made structure, and preventative measures are required. With increasing concern about the polluting impact of the biocides used as antifouling, non-toxic compounds are being sough after. Pertinent to this requirement is the increased interest being given to the potential use of natural biogenic compounds. The present study involves an investigation of the potential antifouling and bactericidal properties of extracts of three species Ralfsia verrucosa, Petalonia fascia and Scytosiphon lomentaria (Scytosiphonales, Phaeophyceae). Methanol and ethanol extracts of these algae were tested for their potential activities against bacteria, microalgae and spores of macroalgae. Bioassays were performed using strains of marine bacteria, human pathogenic bacteria, marine microalgae, freshwater microalgae and marine macroalgae. No antifouling and antibacterial activity was recorded when testing the methanol extracts. Activity was, however, found when using the ethanol extracts. The best activity was obtained with R. verrucosa ethanol extract against Shewanella putrefaciens at a MIC (minimum inhibitory concentration) of 10 µg/mL.