5-Hydroxytryptophan (5-HTP) is an intermediate in the natural synthesis of the essential amino acid, tryptophan, to serotonin. The enzyme tryptophan hydroxylase adds a hydroxyl group (OH) to tryptophan, forming the 5-HTP intermediate. In the body, it converts to serotonin with the removal of a carboxyl group (COOH) by a second enzyme. Serotonin is an important neurotransmitter involved in the regulation of endocrine and brain activity responsible for emotion, appetite and sleep/wake cycles. In clinical studies, administration of 5-HTP supported serotonin production. The 5-HTP supplied in this supplement is derived from the  Griffonia simplicifolia plant.