STRUCTURE AND BIOSYNTHESIS OF NOVEL CONJUGATED POLYENE FATTY-ACIDS FROM THE MARINE GREEN-ALGA ANADYOMENE STELLATA

Novel polyunsaturated fatty acids with four conjugated double bonds we re found in extracts of the green macroalga, Anadyomene stellata. The isolation of five of these with different chain lengths and varying de grees of unsaturation-16:5, 18:4, 20:5, 20:6, and 22:7-was accomplishe d by organic extraction followed by a combination of vacuum and high-p erformance liquid chromatography. One of these that was a novel substa nce (22:7) was characterized as 4Z,7Z,9E,11E,13Z,16Z,19Z-docosaheptaen oic acid and assigned the trivial name stellaheptaenoic acid. The stru cture of this new compound, isolated as its methyl ester derivative, w as deduced from detailed nuclear magnetic resonance, gas chromatograph y/mass spectrometry (GC/MS), and other spectroscopic methods. Incubati on of a chloroplast preparation, isolated from a crude algal homogenat e by differential centrifugation, with six unsaturated fatty acids (pa lmitoleic, 6Z,9Z,12Z,15Z-octadecatetraenoic acid, arachidonic acid, ei cosapentaenoic acid, 7Z,10Z,13Z,16Z-docosatetraenoic acid, and 4Z,7Z,1 0Z,13Z,16Z,19Z-docosahexaenoic acid) resulted in substantially increas ed synthesis of unique tetraene compounds as detected by ultraviolet s pectrophotometry and tentatively identified by GC/MS.