The analysis of pyrrolizidine alkaloids in Jacobaea vulgaris; a comparison of extraction and detection methods.
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.
Joosten
Lotte
L
Ecology and Phytochemistry, Institute of Biology, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands. l.joosten@biology.leidenuniv.nl
Mulder
Patrick P J
PP
Vrieling
Klaas
K
van Veen
Johannes A
JA
Klinkhamer
Peter G L
PG
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*
D011763:Pyrrolizidine Alkaloids