title: The analysis of pyrrolizidine alkaloids in Jacobaea vulgaris; a comparison of extraction and detection methods.
abstract: BACKGROUND
  Pyrrolizidine alkaloids (PAs) serve an important function in plant defence.Objective - To compare different extraction methods and detection techniques, namely gas chromatography with nitrogen phosphorus detection (GC-NPD) and liquid chromatography tandem mass spectrometry (LC-MS/MS) with quadrupole analysers for analysing PAs in Jacobaea vulgaris.
  
  
  METHODS
  Both formic acid and sulfuric acid were tested for PA extraction from dry plant material. For GC-NPD, reduction is required to transform PA N-oxides into tertiary amines. Zinc and sodium metabisulfite were compared as reducing agents.
  
  
  RESULTS
  The lowest PA concentration measured with GC-NPD was approximately 0.03 mg/g and with LC-MS/MS 0.002 mg/g. The detection of major PAs by both techniques was comparable but a number of minor PAs were not detected by GC-NPD. With the LC-MS/MS procedure higher concentrations were found in plant extracts, indicating that losses may have occurred during the sample preparation for the GC-NPD method. Zinc proved a more effective reducing agent than sodium metabisulfite. The sample preparation for LC-MS/MS analysis using formic acid extraction without any reduction and purification steps is far less complex and less time consuming compared to GC-NPD analysis with sulfuric acid extraction and PA N-oxide reduction with zinc and purification.
  
  
  CONCLUSIONS
  In terms of sensitivity and discrimination, formic acid extraction in combination with LC-MS/MS detection is the method of choice for analysing PAs (both free and N-oxides forms) in plant material.
authors.affiliation: Ecology and Phytochemistry, Institute of Biology, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands. l.joosten@biology.leidenuniv.nl
authors.forename: Lotte
authors.initials: L
authors.lastname: Joosten
authors.forename: Patrick P J
authors.initials: PP
authors.lastname: Mulder
authors.forename: Klaas
authors.initials: K
authors.lastname: Vrieling
authors.forename: Johannes A
authors.initials: JA
authors.lastname: van Veen
authors.forename: Peter G L
authors.initials: PG
authors.lastname: Klinkhamer
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D016014:Linear Models; D035261:Plant Components, Aerial / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D011763:Pyrrolizidine Alkaloids / Q000032:analysis*; D012674:Senecio / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D011763:Pyrrolizidine Alkaloids