Determining double-bond positions in monoenoic 2-hydroxy fatty acids of glucosylceramides by gas chromatography-mass spectrometry

We applied a gas chromatography-mass spectrometry (GC-MS) method using dime thyl disulfide (DMDS) adducts and were able to determine the double-bond po sitions in monounsaturated 2-hydroxy fatty acids (2-HFA). 2-HFA methyl este rs, prepared from the hydrolysate of Arabidopsis thaliana leaf glucosylcera mides, were acetylated and methylthiolated. GC-MS analysis of the resulting DMDS adducts showed simple mass spectra with recognizable molecular ions a nd a series of key fragment ions indicating the original double-bond positi ons in the aliphatic chain. Based on this GC-MS elucidation, we confirmed t hat Arabidopsis leaf glucosylceramides have C-22, C-23, C-24, C-25, and C-2 6 chain length 2-HFA with monounsaturation, and all their double bonds are placed at the n-9 position. This procedure is simple, time efficient, and h ighly sensitive.