FATTY ACIDS AND HYDROXY FATTY ACIDS IN THREE SPECIES OF FRESHWATER EUSTIGMATOPHYTES |
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Authors: | John K. Volkman Stephanie M. Barrett Susan I. Blackburn |
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Affiliation: | CSIRO Marine Research, GPO Box 1538, Hobart, Tasmania 7001, Australia |
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Abstract: | The monocarboxylic fatty acids and hydroxy fatty acids of three species of freshwater microalgae—Vischeria punctata Vischer, Vischeria helvetica (Vischer et Pascher) Taylor, and Eustigmatos vischeri (Hulbert) Taylor, all from the class Eustigmatophyceae— were examined. Each species displayed a very similar distribution of fatty acids, the most abundant of which were 20:5n-3, 16:0, and 16:1n-7; C18 polyunsaturated fatty acids were minor components. These fatty acid distributions closely resemble those found in marine eustigmatophytes but are quite distinct from those found in most other algal classes. These microalgae also contain long-chain saturated and unsaturated monohydroxy fatty acids. Two distinct types of hydroxy fatty acids were found: a series of saturated α-hydroxy acids ranging from C24 to C30 with a shorter series of monounsaturated α-hydroxy acids ranging from C26 to C30 together with a series of saturated β-hydroxy acids ranging from C26 to C30. The latter have not previously been reported in either marine or freshwater microalgae, although C30 to C34 midchain (ω-18)-hydroxy fatty acids have been identified in hydrolyzed extracts from marine eustigmatophytes of the genus Nannochloropsis, and C22 to C26 saturated and monounsaturated α-hydroxy fatty acids have been found in three marine chlorophytes. These findings have provided a more complete picture of the lipid distributions within this little studied group of microalgae as well as a range of unusual compounds that might prove useful chemotaxonomic markers. The functions of the hydroxy fatty acids are not known, but a link to the formation of the lipid precursors of highly aliphatic biopolymers is suggested. |
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Keywords: | biomarkers chemotaxonomy Eustigmatophyceae Eustigmatos fatty acids freshwater microalgae long-chain hydroxy acids Vischeria |
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