Improved annotation and quantification of metabolites in rice ( Oryza sativa L.) seeds using two-dimensional gas chromatography–time-of-flight mass spectrometry

Two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS) is a powerful tool for identification of compounds in complex samples. Herein, we compared the GC × GC-TOFMS and GC-TOFMS systems for polar metabolite profiling of rice seeds. Forty-seven and thirty-six metabolites were detected in a Korean rice cultivar, Dongjin, using GC × GC-TOFMS and GC-TOFMS, respectively. The limits of detection of shikimic, p -coumaric, and sinapinic acids were 30.0-, 1.6-, and 2.5-times lower, respectively, with GC × GC-TOFMS than with GC-TOFMS. The overlapped peaks of glycerol and phosphoric acid in GC-TOFMS were separated in GC × GC-TOFMS. Polar metabolite profiling of two white and six red rice cultivars was performed using GC × GC-TOFMS and the obtained data were subjected to principal component analysis. Remarkably, principal component 1 separated Heugdaegu from other cultivars, indicating that Heugdaegu has high levels of caffeic, sinapinic, and vanillic acids. Findings from this work may aid breeding programs aimed at improving the quality of rice seeds.