title: HPLC-ESI-QTOF-MS as a powerful analytical tool for characterising phenolic compounds in olive-leaf extracts.
abstract: BACKGROUND
  Olea europaea L. leaves may be considered a cheap, easily available natural source of phenolic compounds. In a previous study we evaluated the possibility of obtaining bioactive phenolic compounds from olive leaves by pressurised liquid extraction (PLE) for their use as natural anti-oxidants. The alimentary use of these kinds of extract makes comprehensive knowledge of their composition essential.
  
  
  OBJECTIVE
  To undertake a comprehensive characterisation of two olive-leaf extracts obtained by PLE using high-performance liquid chromatography coupled to electrospray ionisation and quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS).
  
  
  METHODS
  Olive leaves were extracted by PLE using ethanol and water as extraction solvents at 150°C and 200°C respectively. Separation was carried out in a HPLC system equipped with a C₁₈-column working in a gradient elution programme coupled to ESI-QTOF-MS operating in negative ion mode.
  
  
  RESULTS
  This analytical platform was able to detect 48 compounds and tentatively identify 31 different phenolic compounds in these extracts, including secoiridoids, simple phenols, flavonoids, cinnamic-acid derivatives and benzoic acids. Lucidumoside C was also identified for the first time in olive leaves.
  
  
  CONCLUSIONS
  The coupling of HPLC-ESI-QTOF-MS led to the in-depth characterisation of the olive-leaf extracts on the basis of mass accuracy, true isotopic pattern and tandem mass spectrometry (MS/MS) spectra. We may conclude therefore that this analytical tool is very valuable in the study of phenolic compounds in plant matrices.
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Granada, c/ Fuentenueva s/n, 18071 Granada, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Quirantes-Piné
authors.forename: Jesús
authors.initials: J
authors.lastname: Lozano-Sánchez
authors.forename: Miguel
authors.initials: M
authors.lastname: Herrero
authors.forename: Elena
authors.initials: E
authors.lastname: Ibáñez
authors.forename: Antonio
authors.initials: A
authors.lastname: Segura-Carretero
authors.forename: Alberto
authors.initials: A
authors.lastname: Fernández-Gutiérrez
mesh_terms: D001565:Benzoates / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D002934:Cinnamates / Q000032:analysis; D004867:Equipment Design; D005419:Flavonoids / Q000032:analysis; D039823:Iridoids / Q000032:analysis; D059625:Liquid-Liquid Extraction / Q000379:methods; D031658:Olea / Q000737:chemistry*; D010636:Phenols / Q000032:analysis* / Q000737:chemistry; D010936:Plant Extracts / Q000032:analysis* / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry*; D059808:Polyphenols / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D001565:Benzoates; D002934:Cinnamates; D005419:Flavonoids; D039823:Iridoids; D010636:Phenols; D010936:Plant Extracts; D059808:Polyphenols; C585295:lucidumoside C; C029010:cinnamic acid