#compounds

The KEGG molecular database as an API, powered by the official KEGG REST service. KEGG (the Kyoto Encyclopedia of Genes and Genomes) links genomes, chemistry and disease. Fetch any KEGG entry parsed to JSON — a metabolic compound, KEGG Orthology group (KO), enzyme (EC number), reaction, module, drug, disease, glycan, gene or pathway map; search any KEGG database by name; list a database's entries; cross-link entries between databases (a gene to its pathways, a pathway to its compounds, an enzyme to its reactions); and convert KEGG identifiers to and from outside namespaces (NCBI Gene/Protein, UniProt, ChEBI, PubChem). Ideal for systems-biology and metabolomics pipelines, enzyme and orthology mapping, drug and disease research, gene-to-pathway annotation and bioinformatics id conversion. KEGG ids are letter-prefixed (C compound, K orthology, D drug, H disease, M module, R reaction, G glycan) or organism-coded (hsa human, eco E. coli).

api.oanor.com/kegg-api

Chemical compound data as an API, powered by NIH PubChem (>100 million compounds). Look up any compound by common name, PubChem CID or SMILES and get its molecular formula, molecular and exact mass, IUPAC name, canonical SMILES, InChI and InChIKey, plus physicochemical properties (XLogP, TPSA, formal charge, hydrogen-bond donor/acceptor counts, rotatable bonds, heavy-atom count). List a compound's synonyms and trade/registry names, or resolve a name to PubChem CIDs. Ideal for cheminformatics, lab software, education, drug-discovery tooling and scientific data pipelines.

api.oanor.com/chemistry-api