Three new unsaturated fatty acids from the marine green alga ulva fasciata delile

From the dichloromethane extract of the marine green alga Ulva fasciata Delile, collected from the Mediterranean coast of Egypt, three new fatty acids, namely, (E)-11-oxo-octadeca-12-enoic acid (1a), (E)-11-hydroxy-octadeca-12-enoic acid (2a) and 6-hydroxy-oct-7-enoic acid (3a) together with cholesterol were isolated. Analysis of the unpolar part of the extract using GC-MS detected the existence of further ten compounds, namely, dimethylsulfoxide, dimethylsulfone, phenylacetamide, 6,10,14-trimethyl-pentadecan-2-one, 8-heptadecene, dodecane, tridecane, 4-oxo-pentanoic acid, hexadecanoic acid, and the naturally new 1,1'-bicyclohexyl. Structures of the isolated compounds 1a - 3a were confirmed by spectroscopic analyses including mass spectra (EI-MS, HR/ESIMS), 1D and 2D NMR experiments, and by the synthetic conversion into their corresponding methyl esters 1b - 3b. The algal extract and its components were comparatively examined against several pathogenic microorganisms, and brine shrimps for cytotoxicity. © 2009 Verlag der Zeitschrift für Naturforschung.