5-HTP (5-Hydroxytryptophan) is a naturally-occurring amino acid extracted from the seeds of Griffonia simplicifolia plant. It is a chemical precursor as well as metabolic intermediate in the biosynthesis of the neurotransmitters serotonin and melatonin from tryptophan. The mood enhancing action of 5-HTP is thought to be derived from its effect on the production of serotonin in the central nervous system tissue.