Profiling and spatial distribution of phenolic compounds in rapeseed by two-step extraction strategy and targeted metabolomics combined with chemometrics.

In this study, a two-step extraction strategy (TSES) and targeted metabolomics combined with chemometrics was successfully applied for profiling of phenolic compounds in different colored rapeseeds. To this end, organic solvent extraction followed by deep eutectic solvent extraction made up the TSES with improved extraction coverage of free phenolics and enhanced extraction yield of conjugated phenolics, which combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) for further profiling of phenolics. TSES-LC-MS/MS method was established with determination coefficients for phenolic compounds greater than 0.9989. Finally, the relationship between color differences and phenolic compounds in rapeseeds was investigated upon TSES-LC-MS/MS method combined with chemometrics. Syringin, kaempferol, isorhamnetin, and sinapic acid were found to be the differential phenolics for the six different colored rapeseeds and their spatial distribution in rapeseeds were presented. Consequently, our method showed great potential for future studies based on comprehensive extraction and profiling of phenolics from complex matrices.