To explore the chemical space of our dataset, molecular weight (MW), logP, and the numbers of hydrogen-bond donor and acceptor (NHBD and NHBA) for all the bitterants and non-bitterants are calculated with Openbabel v2.4 (O'Boyle et al., 2011). The histograms of logP, MW, NHBD, and NHBA are plotted in Figures S1–S4 and the scatter plots of logP vs. MW and NHBA vs. NHBD are shown in Figures 1A,B respectively. Furthermore, the Tanimoto similarity matrix (Figure 2) between bitterants and non-bitterants is calculated based on the 2048bit-ECFP6 due to its more features and less bit collisions.