has role monoamine molecular messenger monamines A group of neurotransmitters and neuromodulators that contain one amino group that is connected to an aromatic ring by ethylene group (-CH2-CH2-). Monoamines are derived from the aromatic amino acids phenylalanine, tyrosine, histidine and tryptophan. CHEBI:25375 monoamines chebi_ontology molecular messenger monoamine