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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).

The Caribbean sponge Smenospongia aurea revealed the presence of six novel branched alpha-hydroxy fatty acids: 2-hydroxy-17-methyloctadecanoic acid, 2-hydroxy-21-methyldocosanoic acid, 2-hydroxy-22-methyltricosanoic acid, and 2-hydroxy-22-methyltetracosanoic acid, 2-hydroxy-24-methylpentacosanoic acid, and 2-hydroxy-23-methylpentacosanoic acid. These novel alpha-hydroxy fatty acids were associated with phosphatidylethanolamine. The sponges Aplysina lacunosa and Aplysina fistularis also contained considerable amounts of alpha-hydroxy fatty acids, the very long-chain 5,9,23-tricontatrienoic acid (30:3), and phytanic acid. The sterol composition of the three sponges was also studied. It indicated that A. lacunosa and A. fistularis contained large amounts of aplysterol and verongulasterol, while S. aurea did not show any of these sterols. The results are discussed in terms of the taxonomy of the species.

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The phospholipid fatty acids from the sponge Cribrochalina vasculum were studied, revealing the presence of the new 23-methyl-5,9-pentacosadienoic acid (26:2) which completes the iso-anteiso 26:2 (delta 5,9) series. Other phospholipid fatty acids isolated include 26-methyl-5,9-heptacosadienoic (28:2) and 25-methyl-5,9-heptacosadienoic (28:2), as well as the branched acids 8-methylhexadecanoic and 11-methyloctadecanoic. The fatty acids described in this work were found in phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. The sterol composition of C. vasculum consisted of petrosterol, an interesting cyclopropane containing sterol, and the more common sitosterol. The phospholipid fatty acid composition of the demosponge Ircinia strobilina is also reported upon.