The principal lipid classes of marine samples. The compounds are subdivided into three groups corresponding to class separations that have been obtained with silica gel thin-layer chromatography on Chromarods (Figure 2; [9]). Each compound structure is drawn with the most hydrophobic part of the molecule pointing towards the right of the figure. (a) The least polar classes: the hydrocarbons and simple esters. Wax esters and steryl esters are difficult to separate on Chromarods. (b) Esters, acids, and alcohols. (c) The most polar and most complex classes: the pigments, monoacylglycerols, glycolipids, and phospholipids.