Fatty acids and hydroxy fatty acids in three species of freshwater eustigmatophytes

The monocarboxylic fatty acids and hydroxy fatty acids of three species of freshwater microalgae-Vischeria punctata Vischer, Vischeria helvetica (Visc her et Pascher) Taylor, and Eustigmatos vischeri (Hulbert) Taylor, all from the class Eustigmatophyceae-were examined. Each species displayed a very s imilar distribution of fatty acids, the most abundant of which were 20:5n-3 , 16:0, and 16:1n-7; C-18 polyunsaturated fatty acids were minor components , These fatty acid distributions closely resemble those found in marine eus tigmatophytes but are quite distinct from those found in most other alg al classes. These microalgae also contain long-chain saturated and unsaturated monohydroxy fatty acids. Two distinct types of hydroxy fatty acids were fo und: a series of saturated alpha-hydroxy acids: ranging from C-24 to C-30 w ith a shorter series of monounsaturated alpha-hydroxy acids ranging from C- 26 to C-30 together with a series of saturated beta-hydroxy acids ranging f rom C-26 to C-30. The latter have not previously been reported in either ma rine or freshwater microalgae, although C-30 to C-34 midchain (omega-18)-hy droxy fatty acids have been identified in hydrolyzed extracts from marine e ustigmatophytes of the genus Nannochloropsis, and C-22 to C-26 saturated an d monounsaturated alpha-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 mark ers. 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 su ggested.