Fig. 4

B. mori cocoon shell metabolomics. (a) Heat map of signal intensity fractions of all the 141 identified metabolites, in all the 80 samples that were analysed. (b) A circus plot displaying the proportion of each super-class of metabolites in relation to the age or the cocoon shell or the presence/absence of colour. (c) Decision tree analysis⁴⁷ showing the chemical structure of Fumaric acid and the signal intensity fraction above or below which old or contemporary samples can be distinguished. (d) Validation for the presence of flavonoids in the 148 cocoon shell samples. The results are expressed as rutin equivalents. (e) Validation of the presence of free amino acids in cocoon shells³³. A set of 10 contemporary (Upper 10 labels on the Y-axis) and 10 old (Lower 10 labels on the Y-axis) cocoon shell samples were analysed for the presence of 18 free amino acids (X-axis) as identified in the metabolomics analysis (see Fig. 4a). The heatmap shows the content of each amino acid expressed as Log of μg per cocoon shell. No statistically significant differences (p > 0.05) were recorded in the free amino acids contents between the two groups of cocoon shells.