The REtrosynthetic Combinatorial Analysis Procedure (RECAP) algorithm, implemented in the RDKit package, was used to generate the molecular fragments in the studied databases. RECAP algorithm fragments molecular structures around bonds formed by common chemical reactions. Recognized cleavable bonds for the RECAP algorithm are amide, ester, amine, urea, ether, olefin, quaternary nitrogen, aromatic carbon, and sulphonamide. Those rules are applied for acyclic bonds, while rings are maintained intact. In the present work, we compared the content of fragments of NPs lighter than 1350 g/mol in NAPROC-13 (21226 compounds) with those generated from NPs lighter than 1000 g/mol in UNPD-A (14733 compounds) and FDA-approved drugs lighter than 2000 g/mol (2317 compounds). MW filtering was applied to reduce the computational cost, and the benchmark was designated according to the time of computation related to the molecular complexity. The newly generated fragment library is freely available at . Finally, molecular descriptors related to the rule of three (RO3) were computed using the Datamol Python library, version 0.12.3.