has role octadecanoid anion octadecadienoate 279.4393 279.23241 -1 A long-chain, unsaturated fatty acid anion formed by deprotonation of the carboxy group of any octadecadienoic acid; major species at pH 7.3. chebi_ontology CHEBI:25626 [O-]C([*])=O C18H31O2 octadecadienoate octadecadienoic acid polyunsaturated fatty acid anion human metabolite