Nontargeted Profiling of Specialized Metabolites of Digitalis purpurea with a Focus on Cardiac Glycosides

摘要

There is an urgent need to develop rapid and powerful tools for structural annotation and natural product identification to support the discovery of genes involved in specialized metabolite accumulation. In this study, nontargeted profiling of metabolites from tissues of the medicinal plant Digitalis purpurea was exploited. Application of liquid chromatography/time-of-flight mass spectrometry (LC-TOF MS) with multiplexed collision-induced dissociation (CID) generated molecular and fragment ion masses to support metabolite identification. Twenty-nine metabolites extracted from various tissues were annotated as steroidal glycosides, on the basis of mass measurements of pseudomolecular and fragment ions in conjunction with previous reports of steroidal glycosides in Digitalis tissues. The MS/MS spectra obtained by hybrid triple quadrupole-linear ion trap (QTrap) MS were complemented by accurate pseudomolecular mass measurements generated with TOF MS and fragment ion masses generated by quasi-simultaneous collision voltage. These combined methods permitted the metabolite profiling of cardiac glycosides and the tentative identification of a novel cardiac glycoside.