Sterol and fatty acid composition of four marine haptophycean algae

Abstract

The lipids of four marine coccolithophorids (class Haptophyceae),Emiliania huxleyi, Hymenomonas carterae, Isochrysis galbanaandCrystallolithus hyalinus, were examined by capillary gas chromatography-mass spectrometry. Fatty acids ranged from C14to C22and were predominantly of even chain length. The major acids were polyunsaturated C18acids, 22:6 and either 14:0 or 16:0. C20fatty 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 inE. 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. carteraeandC. hyalinusalso contained 24-ethylcholesta-5,22E-dien-3β-ol and significant amounts of cholest-5-en-3β-ol were found inE. huxleyiandI. galbana. An unusual sterol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, was identified inH. carterae. These sterols were mostly non-esterified although small amounts of sterol esters were identified inE. huxleyi. The lipid composition ofE. huxleyiis distinctive in that it contains, in addition to the C36fatty acid, novel C37–C39unsaturated ketones and C31–C38alkenes. Of the other coccolithophorids onlyI. galbanacontained small quantities of one of the C3lalkenes.