Identification of the Novel Antimicrobial Fatty Acid (5Z,9Z)-14-Methyl-5,9-pentadecadienoic Acid in Eunicea succinea

The phospholipid fatty acid composition of Eunicea succinea was investigated, and the novel (5Z,9Z)-14-methyl-5,9-pentadecadienoic acid was identified. Structural characterization was accomplished by means of mass spectrometry of its pyrrolidide derivative, NMR, FT1R, and total synthesis. Other interesting phospholipid fatty acids in E. succinea were the tetracosapolyenoic acids 6,9,12,15,18,21-tetracosahexaenoic acid (24:6) and 6,9,12,15,18-tetracosapentaenoic acids (24:5). The title compound was particularly active against Gram-positive bacteria such as Staphylococcus aureus (MIC 0.24 mumol/mL) and Streptococcus faecalis (MIC 0.16 mumol/ mL).