Sulfur-Omics in Health-Promoting Crops: Unearthing Sulfur-Containing Metabolites By Using Liquid Chromatography-Fourier Transform Ion Cyclotron Resonance-Mass Spectrometry

Sulfur-containing metabolites (S-metabolites) in multifold health-promoting crops have a wide range of beneficial biological activities to human. We have therefore constructed a practical profiling method for S-metabolites using liquid chromatography‒Fourier transform ion cyclotron resonance‒mass spectrometry (LC‒FTICR‒MS: LC, Agilent 1200 series; MS, Bruker Daltonics solariX 7.0 T), so called S-omics¹. Here, we present the application of S-omics to 40 plants including Brassicaceae, Alliaceae, and Solanaceae plants to discover S-metabolites. Freeze-dried samples were extracted with 80% Methanol containing an internal standard (lidocaine). The extract solutions were analysed in the positive mode of the LC‒FTICR‒MS system to acquire MS and MS/MS spectra. The raw data were converted to netCDF files² and were stored in the database HIFI (Heteroatom-containing Ion Finder) in PRIMe (http://prime.psc.riken.jp/) to pick up S-containing ions (S-ions) derived from S-metabolites. As a result, a series of S-ions from known specialized (secondary) metabolites such as glucosinolates, S-alk(en)ylcysteine sulfoxides, and glutathione derivatives were successfully picked up as positive controls in this analysis together with candidate ions of novel S-metabolites. These results suggest that S-omics is applicable to the study of crop breeding and phytochemical genomics to understand biosynthetic mechanism for S-metabolites. 

REFERENCES

1. Nakabayashi et al., Combination of liquid chromatography-Fourier transform ion cyclotron resonance-mass spectrometry with 13C-labeling for chemical assignment of sulfur-containing metabolites in onion bulbs. Anal. Chem.85:1310-1315.

2. All netCDF files acquired by LC‒FTICR‒MS will be deposited at DROP Met in PRIMe and be freely available.