Lipid and Fatty Acid Composition of the Marine Brown Alga Dictyopteris membranacea

Glycerolipids and fatty acids of D. membranacea (Dic-tyotales)were analysed. The betaine lipid DGTA and the glycolipids MGOG,DGDG and SQDG were major components. The phospholipids PE, PG,PI and PHEG were present in minor amounts only. This lipid pattern,which is characterised by the presence of DGTA and the absenceof PC, has been found exclusively in brown algae belonging tothe orders Dictyotales, Durvillaeales and Fucales. Major fattyacids were 16:0, 18:1, 18:2, 18:3, 18:4 and 20:4 acids. MGDGwas the most unsaturated lipid with high levels of 18:4 acid.SQDG showed the highest degree of saturation containing a considerableproportion of 16:0 acid. DGTA contained 14 : 0,18:1,18:2 and20:4 as major fatty acids. Among phospholipids, PE and PHEGhad a very similar pattern which was enriched in 20:4 acid.Analysis of the positional distribution of fatty acids revealedthat DGTA and MGDG were almost exclusivly of the "euka-ryotic"type, whereas SQDG was predominantly of the "prokaryotic" type.For the first time, molecular species of selected lipids havebeen analysed in a brown alga. In DGTA, 14:0/18:1, 14:0/18:2and 14:0/20:4 were the main molecular species. In MGDG the highlyunsaturated erl8:3/18:4, 18:4/18:4 and 18:4/20:5 were predominant. (Received March 31, 1997; Accepted July 4, 1997)