Metabolite profiles between rectal cancer tissues and normal controls. A PCA scores plot discriminates metabolites from the rectal cancer tissues and normal controls using 1H NMR. B OPLS-DA scores plot based on same samples. C The color map shows the significance of metabolite variations between the two classes. Peaks in the positive direction indicated the increased metabolites in rectal cancer tissues in comparison to normal control. Deceased metabolites in rectal cancer tissues were presented as peaks in the negative direction. D Statistical validation of the corresponding PLS-DA model using permutation analysis (200 times). R2 is the explained variance, and Q2 is the predictive ability of the model.