5-hydroxytryptophan is a tryptophan derivative that is tryptophan substituted by a hydroxy group at position 5. It has a role as a human metabolite and a neurotransmitter. 5-Hydroxytryptophan, DL- is a racemic mixture of 5-hydroxytryptophan (5-HTP), a precursor to the neurotransmitter serotonin with anti-depressant, analgesic and appetite ...