Introduction - 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. Methodology - 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 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, L., Mulder, P. P. J., Vrieling, K., Van Veen, J. A., & Klinkhamer, P. G. L. (2010). The analysis of pyrrolizidine alkaloids in Jacobaea vulgaris; a comparison of extraction and detection methods. Phytochemical Analysis, 21(2), 197-204. https://doi.org/10.1002/pca.1183