Transgenic Arabidopsis plants were analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) to investigate the glycosylation patterns of resveratrol derived from expression of a sorghum stilbene synthase gene. In negative ionization mode, the different resveratrol derivatives fragmented to yield the diagnostic deprotonated resveratrol ion at m/z 227.2. The use of precursor ion scanning led to the identification of precursor ions for different resveratrol glycosides through rapid differentiation from other phytochemical constituents. Structural information was generated simultaneously from the low-collision-energy product ion spectra using hybrid linear ion-trap mass spectrometry. Three additional resveratrol-related metabolites - a resveratrol diglucoside (M1) and trans- and cis-resveratrol acetylhexosides (M2 and M3) - were detected in the crude plant extracts. The identities of M1, M2, and M3 were confirmed by accurate mass analysis on a quadrupole time-of-flight mass spectrometer as well as beta-glucosidase digestion or UV-induced isomerization. Quantitative analyses by LC/MS in multiple reaction monitoring mode revealed that resveratrol diglucoside and cis-resveratrol acetyhexoside accumulated up to 2.79 and 10.38 microg/g, respectively, while trans-resveratrol acetylhexoside was barely detectable. This study demonstrated the power of the hybrid linear ion-trap technology for simultaneous profiling and structural characterization of stilbene-related metabolites, which would be useful to understand how resveratrol is modified in sorghum and other plants.
Copyright (c) 2007 John Wiley & Sons, Ltd.