Targeted analysis of ceramides and cerebrosides in yellow lupin seeds by reversed-phase liquid chromatography coupled to electrospray ionization and multistage mass spectrometry

Abstract

Ceramides (Cer) and cerebrosides are important sphingolipids (SL) involved in many biological processes. Herein, the SL content of yellow lupin seeds (Lupinus luteus) was determined by liquid–liquid extraction, mild alkaline hydrolysis (1 h at 37 °C) and reversed-phase liquid chromatography with negative electrospray ionization coupled to either an orbital-trap (Fourier-transformed, FT) or linear ion-trap (LIT) mass spectrometry (RPLC-ESI/MS). The chemical identity of SL including the sugar residues and sphingoid backbone (SB) was inferred by collision-induced dissociation multiple-stage mass spectrometry (MSn, n = 2,3). Up to 52 Cer and 47 cerebrosides were successfully recognized and quantified in sample extracts of L. luteus seeds also counting isobaric species. As reported for other vegetables, a hydroxylated SB was observed whereby the N-acyl chains showed a high occurrence of very-long-chain moieties; phytosphingosine and 4-hydroxy-8-sphingenine were the predominant SB paired mainly with oleic acid (C18:1), hydroxylated behenic acid (C22:0;1) and hydroxylated lignoceric acid (C24:0;1).