CHEBI

http://www.ebi.ac.uk/chebi/

“A freely available dictionary of molecular entities focused on ‘small’ chemical compounds.” CHEBI draws its information from two main sources: Integrated Relational Enzyme Database of the EBI and the Kyoto Encyclopedia of Genes and Genomes. Find out what proteins a molecule has been associated with and in what context. Provides cross-links to CAS registry numbers, Beilstein registry numbers, and Gmelin registry numbers