Figure 6. Box-plot comparison of the concentrations associated with the most relevant metabolites involved in the discrimination based on gender. Concentration values are normalized to total intensity. Values are represented as mean±SEM. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001. P-values were calculated with a Student’s t-test. For each box, the central line is the median, the edges of the box are the upper and lower quartiles, the whiskers extend the box by a further ±1.5 interquartile range (IQR) and outliers are plotted as individual points. M: men, W: women, ATP: adenosine triphosphate.