Structure of digalactosyldiacylglycerol from oats.

Digalactosyldiacylglycerol (DGalDAG) is one of the major lipids in the cells of higher plants. DGalDAG forms a lamellar liquid crystalline phase together with water. Lipid aggregates can thus be prepared which are of potential interest for use within the cosmetic and pharmaceutical industries. Oats may be an important source for preparation of DGalDAG, but the structure has not been determined for the DGalDAG lipid occurring in this plant. In the present study the structure of a high-purity DGalDAG preparation, isolated from commercial oat flakes, was determined by high resolution 1H- and 13C-NMR spectroscopy. The lipid was found to have the structure 1,2-diacyl-3-O-[alpha-galactopyranosyl-(1-->6)-O-beta-galactopyranosyl]- glycerol. By using 1H- and 13C-NMR spectroscopy techniques it is thus possible to determine, among other things, the identity of the glycosyl moieties in the polar head group, to establish the linkage positions between these moieties, and to establish the anomeric configurations of the moieties, without making any chemical modifications of the lipid.