Characterization of isomers of oleuropein aglycon in olive oils by rapid‐resolution liquid chromatography coupled to electrospray time‐of‐flight and ion trap tandem mass spectrometry

Abstract

In this work, rapid-resolution liquid chromatography (RRLC) coupled to electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) and ion trap multiple mass spectrometry (IT-MS(n)) has been applied to separate and characterize eleven isomers of oleuropein aglycon in fourteen Spanish extra-virgin olive oils. After the extra-virgin olive oil sample had been dissolved in hexane and cleaned up by a diol-bonded phase solid-phase extraction (SPE) cartridge, the eluting extract was resolved in methanol and analyzed on an Angilent 1200 system with a 4.6 x 150 mm, 1.8 microm Zorbax Eclipse plus C18 column. Mass spectrometry was carried out on a Bruker Daltonics microTOF mass spectrometer and a Bruker Daltonics ion trap mass spectrometer. The characterization of isomers of oleuropein aglycon was based on accurate mass data and the isotope function of characteristic fragment ions in the studied compounds by TOF-MS, and the fragment ions were further confirmed by IT-MS(n). The fragmentation pathway of oleuropein aglycon was successfully elucidated and all possible transformations among isomers of oleuropein aglycon were suggested.