Antibacterial activity of Indonesian red algae <i>Gracilaria edulis</i> against bacterial fish pathogens and characterization of active fractions

<p>In this study the crude ethyl acetate extracts and fractions from red algae <i>Gracilaria edulis</i> were studied against fish pathogens. <i>G. edulis</i> was extracted with ethyl acetate, fractionated in silica gel coloum chromatography and gradient hexane-ethyl acetate. The extract and fractions were subjected for bioassay guided isolation against fish pathogen <i>Vibrio</i> spp and <i>Aeromonas hydrophila</i>. Bioassays were accomplished by diffusion agar, bioauthography, and 96 well microplates format. Profiling chemical constituent was done by thin layer chromatography and GC-MS. Metabolites analysis using GC-MS yielded chemical constituents of active fractions as 9-hexadecenoic acid, hexadecanoic acid, 13-octadecenoic acid, 10-octadecenoic acid, eicosanoic acid, cholest-8-en-3-ol. The results provide <i>in vitro</i> scientific support to the possible application of <i>Gracilaria edulis</i> as antimicrobial agent that may contribute for treatment of bacterial infections in aquaculture.</p>