A derivatization procedure for the simultaneous analysis of iminosugars and other low molecular weight carbohydrates by GC-MS in mulberry (Morus sp.)

Different derivatization procedures were assayed to simultaneously analyse iminosugars such as deoxynojirimycin (DNJ) or fagomine and other carbohydrates of low molecular weight by gas chromatography coupled to mass spectrometry (GC-MS) in Morus sp. Both oximation + trimethylsilylation and oximation + acetylation allowed the separation of target compounds, whereas trimethylsilyl (TMS) and acetylated derivatives showed several coelutions. Nevertheless, oximation + acetylation were discarded for giving inaccurate results for ketoses due to their incomplete derivatization. Different conditions for the conversion into trimethylsilyl oximes (TMSO) were assayed, the best results being achieved using hexamethyldisilazane with trifluoroacetic acid as silylation agent. Contents of iminosugars (DNJ, fagomine and pipecolic acid derivatives) and other carbohydrates such as mono and disaccharides, myo-inositol and galactinol isomers in mulberry extracts (fruits, leaves and branches) were determined by GC-MS using the TMSO procedure.