Metabolite profiling of chalcones and flavanones in tomato fruit

Tomato (Solanum lycopersicum) is one of a group of plants that accumulate chalcones and flavanones. However, the molecular diversity of chalcones, flavanones, and their conjugate metabolites has not been investigated intensively. Here, we report the profiling of chalcones and flavanones in fruits of the dwarf tomato cultivar MicroTom using liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR-MS). We identified eriodictyol chalcone and eriodictyol aglycones, along with naringenin chalcone and naringenin aglycones. To our knowledge, this is the first report that demonstrates the presence of eriodictyol chalcone and eriodictyol in tomato. We detected 26 conjugate metabolites of chalcones and flavanones. Chemical information obtained simultaneously by LC-FTICR-MS, including m/z values, MS/MS spectra, UV absorption spectra, and retention times, facilitated the elucidation of molecular formulas and conjugate structures of the metabolites. Eriodictyol chalcone and eriodictyol conjugates had the same modification patterns seen in naringenin chalcone and naringenin conjugates. Chalcones and flavanones were much more abundant in tomato fruit peel than flesh. Accumulation profiles during ripening were classified into three groups. The first group included metabolites that showed the highest accumulation levels at the breaker stage, and then decreased during ripening. The second group included metabolites that accumulated to the highest levels at the turning stage, and then decreased at the red stage. The third group included metabolites that accumulated gradually during ripening, and showed the highest accumulation levels at the red stage. These accumulation profiles were mapped onto a putative modification pathway deduced from conjugate structures. Mapping revealed that the conjugate metabolites upstream of this pathway accumulated earlier, and those downstream accumulated later during ripening. This result demonstrated that chalcones and flavanones undergo sequential modification as ripening progresses.