Quantitative analysis of pyrrolizidine alkaloids in Gynura procumbens by liquid chromatography-tandem quadrupole mass spectrometry after enrichment by PCX solid-phase extraction

Gynura procumbens is commonly consumed as a vegetable and has been approved as an ingredient for food and dietary supplements in China. However, Gynura species are known to contain toxic pyrrolizidine alkaloids (PAs) and the PA profiles in G. procumbens are not known. This study was to extract and enrich PA from G. procumbens or health care products using PCX solid-phase extraction (SPE) cartridges identify the main PAs in the herb and to develop an liquid chromatography-mass spectrometry (LC-MS/MS) method for assaying the PA contents in the plant and its derived products. Upon using multiple reaction monitoring (MRM) acquisition together with comparison to the characteristics of mass fragmentations and retention times of reference standards, 11 PAs were identified as the main PAs in the plant. After clean-up and enrichment with PCX solid-phase extraction (SPE) cartridges, which resulted in better PA recoveries than either C18 or SCX cartridges, the LC-MS/MS method was subjected to validation in terms of linearity, repeatability, limits of quantification (LOQ) and recovery. The validated method was applied to quantify PAs in 12 plant samples and 7 commercial finished products. The total amounts of targeted PAs were found to vary from 15.6 to 848 mu g/kg in the herbs and from 9.9 mu g/kg to 33.9 mg/kg in the commercial products. The present work was the first to demonstrate that G. procumbens contained PAs in the herb and its derived products and the PA contents might exceed the daily dose limits in food and herbal medicinal products proposed by the European Medicines Agency (i.e. 0.35 mu g PA per day for 50 kg adult).