Doctor's Best 5-HTP is a naturally occurring metabolite of the amino acid tryptophan. 5-HTP (5-hydroxy L-tryptophan) is converted in the brain to serotonin, a neurotransmitter substance found at the junctions (synapses) between neurons. 5-HTP helps maintain mental and emotional well-being and promotes healthy sleep. Doctor's Best 5-HTP is extracted from the seeds of the Griffonia Simplicifolia plant.