Sterol and fatty acid composition of four marine haptophycean algae

The lipids of four marine coccolithophorids (class Haptophyceae), Emiliania huxleyi, Hymenomonas carterae, Isochrysis galbana and Crystallolithus hyalinus , were examined by capillary gas chromatography-mass spectrometry. Fatty acids ranged from C 14 to C 22 and were predominantly of even chain length. The major acids were polyunsaturated C 18 acids, 22:6 and either 14:0 or 16:0. C 20 fatty acids were of low abundance. Significant amounts of octadecapentaenoic acid (18:5), previously thought to be unique to dinoflagellates, were identified in three of the algae. A small amount of a di-unsaturated C36 w-alkenoic acid was identified in E. huxleyi , which is the first report of such a long-chain fatty acid in any alga. Traces of wax esters, which are reportedly uncommon inalgae, were found in three of the species. The sterol distributions were very simple, with two or three compounds accounting for > 99% of the total sterols. In each case, the major component was 24-methylcholesta-5,22E-dien-3β-ol. H. carterae and C. hyalinus also contained 24-ethylcholesta-5,22E-dien-3β-ol and significant amounts of cholest-5-en-3β-ol were found in E. huxleyi and I. galbana . An unusual sterol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, was identified in H. carterae . These sterols were mostly non-esterified although small amounts of sterol esters were identified in E. huxleyi . The lipid composition of E. huxleyi is distinctive in that it contains, in addition to the C 36 fatty acid, novel C 37 –C 39 unsaturated ketones and C 31 –C 38 alkenes. Of the other coccolithophorids only I. galbana contained small quantities of one of the C 3l alkenes.