Rapid analysis of medically relevant compounds in faba bean seeds using FAIMS and mass spectrometry

Abstract

Faba bean (Vicia faba L.) has potential to expand globally because of its ability to provide nutritional benefits through its high amounts of seed protein, carbohydrates and dietary fiber. The seeds also contain levodopa, a treatment for Parkinson’s disease. Faba bean consumption is limited primarily because the seeds contain the pyrimidine glycosides, vicine and convicine (v-c), which can cause favism in people with a genetically inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency. G6PD deficiency is inherited as an X–linked recessive allele and susceptible individuals develop anaemia when they consume faba beans. Faba bean cultivars with reduced levels of v-c are available, but it is difficult to maintain genetic isolation because the plants can be cross-pollinated by bees. The seed supplies of low v-c seed stocks and foods derived from them must be monitored to ensure maintenance of low v-c. Here we report a rapid, robust method to measure vicine, convicine, and levodopa using high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled with flow injection analysis and mass spectrometry that has an analysis step of 54 s. With the addition of a methanol gas modifier in FAIMS, vicine and convicine were separated in the gas-phase and then measured by tandem mass spectrometry. More than 40 genotypes representing diverse faba bean germplasm were quantified. Convicine showed the widest concentration range (~520X) and all analytes showed good reproducibility illustrating that this method can be routinely used to simultaneously screen for v-c and quantify L-DOPA, thereby ensuring food safety.