<p> Colonies of the soft coral Sinularia polydactyla collected from the vicinity of Panjang island, Jepara region, Central Java, Indonesia were tested to examine their antibacterial properties. </p> <p> Chemical analysis and bioassay-directed purification by repetitive column chromatography using Vibrio harveyi as tester strain revealed that S. polydactyla possesses antibacterial properties against this test strain. Purification gives a mixture of esters, which inhibited the growth of the marine biofilm forming bacterium, V. harveyi with an EC50 value of 0.075 mg/10 mL of culture medium. </p> <p> Chemical synthesis of the esters Hexadecyl palmitate (1 ), hexadecyl stearate (2), octadecyl palmitate (3), and octadecyl stearate (4) was accomplished from the alcohols and fatty acid acyl halides. Each purified ester was characterized by NMR and MS. Comparison of the MS for these authentic synthetic samples with that for the biologically derived sample showed that the latter was composed predominantly of esters 1 and 3. The individual esters were tested against V. harveyi. Compound 1 was active and 4 was less active, while 2 and 3 were inactive. Hence, 1 is the major active compound against V. harveyi in the natural mixture. </p> / Thesis / Master of Science (MSc)