Characterization of phytochemicals from twisted-leaf garlic (Allium obliquum L.) using liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

Introduction Twisted-leaf garlic (Allium obliquum L.) is a wild Allium species, which is traditionally used as aroma plant for culinary purposes due to its unique, garlic-like favor. It represents an interesting candidate for domestication, breeding and cultivation. Objectives The objective of this work was to explore and comprehensively characterize polar and semi-polar phytochemicals accumulating in leaves and bulbs of A. obliquum. Method Plant material obtained from a multiyear feld trial was analyzed using a metabolite profling workfow based on ultra-high performance liquid chromatography-coupled electrospray ionization quadrupole time-of-fight mass spectrometry (UHPLC/ESI-QTOFMS) and two chromatographic methods. For annotation of metabolites, tandem mass spectrometry experiments were carried out and the resulting accurate-mass collision-induced dissociation (CID) mass spectra interpreted. Onion and garlic bulb extracts were used as reference samples. Results Important metabolite classes infuencing nutritional, sensory and technological properties were detected and structurally characterized including fructooligosaccharides with a degree of polymerization of 3–5, S-alk(en)ylcysteine sulfoxides and other S-substituted cysteine conjugates, favonoids including O- and C-glycosylated favones as well as O-glycosylated favonols, steroidal saponins, hydroxycinnamic acid conjugates, phenylethanoids and free sphingoid bases. In addition, quantitative data for non-structural carbohydrates, S-alk(en)ylcysteine sulfoxides and favonoids are provided. Conclusion The compiled analytical data including CID mass spectra of more than 160 annotated metabolites provide for the frst time a phytochemical inventory of A. obliquum and lay the foundation for its further use as aroma plant in food industry