Of the 174 curated reactions, 143 were not already listed in the PubChem Transformations library and 31 were listed but with different associated metadata (e.g., different biosystem, enzyme, or evidence description). In addition, 18 of the curated TP structures were not yet present in PubChem and were deposited as a part of this work (CIDs 167530376-167530379 and 168354689 to 168354702). This shows that much of the information available for curation in the Metabolism and Metabolites section of PubChem is not already available in the Transformations library, such that curating this information as done here can help fill significant knowledge gaps in the database. This may then further improve the extraction of reaction rules and the development of machine learning models for transformation product prediction. Some examples of TPs curated with ShinyTPs include benzidine and congeners, formed by benzidine-derived azo-dyes as depicted in Figure . Based on these reactions it was possible to derive some reaction rules such as the cleavage of the nitrogen-nitrogen double bond followed by acetylation of the amino-groups. Several of the benzidine and congeners have also been found to be carcinogenic and/or mutagenic, indicating that other dyes containing the substructure highlighted in blue in Figure may also form hazardous TPs.