File Name : figure s1.tif

Caption : figure s1. maldi-tof ms mass spectra of reference <i>s. senegal </i>combined with (a) calcite, (b) malachite, (c) iron oxide, and (d) orpiment, mass range 800-1300 da. only the <i>m/z</i> values of diagnostic ions are reported in the spectra. for the list of diagnostic ions of <i>s. senegal</i> see granzotto et al. 2017.<sup>3</sup>

File Name : figure s2.tif

Caption : figure s2. pca scores plot (pc1 vs pc2) with legend of maldi-tos ms data of reference acacieae samples, including the pigmented <i>s. senegal</i> samples (dark green plus sign).

File Name : figure s3.tif

Caption : figure s3. pca scores plot (pc1 vs pc3) with legend of maldi-tof ms data of reference acacieae samples and historic samples. <i>v. tortilis</i>, <i>v. nilotica</i> and samples from artworks are labeled.