The molecular scaffolds were generated using the Bemis-Murcko definition using RDKit . We calculated the proportion of scaffolds relative to the number of compounds (N/M). Based on Cyclic System Retrieval (CSR) curves, we calculated the area under the curve (AUC) and the fraction of chemotypes that recover 50% of the molecules in the data set (F50). The Shannon entropy of the ten most frequent scaffolds was also calculated . To identify possible unique scaffolds, the unique scaffolds of each database were compared with each other.