5-Hydroxytryptophan (5-HTP) is an intermediate in the natural synthesis of serotonin from the essential amino acid tryptophan. The enzyme tryptophan hydroxylase adds a hydroxyl group (OH) to tryptophan, forming the 5-HTP intermediate. In the body, 5-HTP is converted to serotonin with the removal of a carboxyl group (COOH) by a second enzyme. 5-HTP is involved in the regulation of endocrine and brain activity responsible for emotion and sleep/wake cycles. In clinical studies, administration of 5-HTP has been reported to improve rapid eye movement (REM) sleep duration and promote emotional well-being. The 5-HTP supplied in this supplement is derived from the Griffonia simplicifolia plant.