Molecular Networking and Equivalently Quantitative Ion Strategy for Discovery and Quantification of Glucosinolates in Cauliflower and Broccoli by Liquid Chromatography Tandem Mass Spectrometry

Glucosinolates (GSLs) are unique secondary metabolites in cauliflower and broccoli, which have diverse biological activities. In this study, a molecular networking combined with the equivalently quantitative ion strategy was built based on liquid chromatography tandem mass spectrometry (LC-MS/MS) for the discovery and quantification of GSLs in cauliflower and broccoli. Firstly, 19 GSLs were identified including 2 new compounds, 4-hydroxyneoglucobrassicin and gluco-4-hydroxyneoglucobrassicin. Moreover, the shared fragment ion m/z 96.0 was set as the equivalently quantitative ion to quantify GSLs. This method could use only one reference standard (or one calibration curve) to efficiently quantify all aliphatic and phenyl GSLs in cauliflower and broccoli. This method was fully validated with good linearity, recovery and sensitivity, and subsequently applied in GSLs quantification. The developed strategy could also be applied in GSLs discovery and quantification in other Brassicaceae vegetables.