Exploitation of plant residues: extraction, separation and characterisation of glycosylceramides

Ceramides play a significant role in the formation and stability of the skin barrier as major component (35 – 40%) of the stratum corneum, the outermost layer of human skin. Additionally they function in signal transduction and cell-cell-recognition processes in the human body, e.g. ceramides may induce apoptosis in human colon-carcinoma cells. Ceramides (Fig. 1) belong to the complex class of sphingolipids and consist of a sphingoid backbone that is acylated with a fatty acid. They occur in all animals, plants and fungi, but also in prokaryotes and viruses.

Fig. 1: Representative structure of glycosylceramides in plants

The complex sphingolipid consists of (1) a sphingoid base, (2) a fatty acid and (3) a polar head group-moiety. Glycosylceramide (d18:2 h16:0) is shown as example. Each component may undergo further modifications.

Plant and human ceramides vary in their structure. In contrast to human ceramides, those of plant origin are mostly glycosylated (Fig. 1). The various functions of those glycosylceramides in plants are still to be elucidated.

The extraction of vegetable wastes seems to be an attractive way to obtain glycosylceramides for further experiments on the role of “phyto”-ceramides in the plants themselves and for possible applications in health care and therapy.

This study concentrates on wheat germ, a by-product of wheat milling. Wheat germ was found before to be a rich source of glycosylceramides. The lipid fraction was extracted quantitatively. Next, a purification method was developed using TLC-guided column chromatography on polar silica gel. Finally, glycosylceramide containing fractions were analysed and structurally characterised by HPLC/APCI-MS.