Best l-tryptophan products contain ajinomoto tryptopure. tryptophan is an essential amino acid readily converted by the body to the neurotransmitter serotonin. able to cross the blood-brain barrier, l-tryptophan is altered by enzymes to first form the intermediate amino acid 5-htp and then serotonin. it is also the metabolic precursor to melatonin and to the b vitamin niacin. supplementing the diet with pure l-tryptophan like tryptopure™, found in doctor’s best l-tryptophan products, can improve sleep and enhance mood, and may also be beneficial in reducing carbohydrate cravings.*