Fig. 2

Quality analysis and metabolites annotation of metabolomics data in Control, EMCI and LMCI groups. A: Venn diagram of the differential metabolites. The overlapping part indicated the same amounts of metabolites among groups. B: PLS-DA score plot. The x-axis and y-axis represented the explanatory degree of the first (Component1) and the second (Component2) principal components, respectively. C: PLS-DA permutation test was used to verify the fitting effect of the model. The x-axis represented the retention of permutation test, the y-axis represented the values of R2 (red dot) and Q2 (blue triangle) permutation test, and the two dotted lines respectively represented the regression lines of R2 and Q2. D: Traceability analysis of metabolites. The x-axis represented the source of metabolites; The y-axis represented the number of metabolites. E: KEGG compound classification. The y-axis was KEGG compound classification, and the x-axis was the number of compounds annotated to corresponding types; The color of the bar indicated the primary class of the compound to which they belonged. F: KEGG pathway analysis. The y-axis was the secondary classification of KEGG metabolic pathway, and the x-axis was the number of compounds annotated to this pathway