Application of UHPLC-Q-TOF MS based untargeted metabolomics reveals variation and correlation amongst different tissues of Eucommia ulmoides Oliver

The biological function of Eucommia ulmoides Oliver (EU) is related to its metabolites. However, due to the complexity of distribution of metabolites in different tissues, currently, the comprehensive information analysis on metabolome of EU has been limited. In this study, we analyzed the components of leaves, seeds and barks of EU by using ultra high-performance liquid chromatography-tandem time-of-flight mass spectrometer (UHPLC-Q-TOF MS) untargeted metabolomics before 2373 metabolites were identified in total. By using Principal Component Analysis (PCA), Partial Least Square Discriminant Analysis (PLS-DA) and other multivariate statistical analysis methods, there were 116 metabolites expressing differently in all samples. The result showed that the metabolic composition of leaves was similar to that of barks and there still existed significant differences amongst different tissues in HCA analysis. Besides, the heatmap of differential metabolites also showed the higher concentrations of organic acids and derivatives, lipids and lipid-like molecules in seeds compared to leaves and barks. Furthermore, we detected 13,456 metabolites-metabolites correlations and determined 1098 metabolic pairs which resulted in significant correlation by Pearson’s correlation analysis. At last, all detected metabolites were annotated in KEGG and 966 of them had KEGG ID. After enrichment analysis, 311 metabolites were mapped in 168 pathways and 26 of these pathways had apparent influence in the metabolic differences amongst different parts of EU. This work provides the first comprehensive metabolomic of EU, which will provide theoretical basis for the separation and identification of medicinal activities of EU and potentially help advance studies in EU metabolic engineering.