L-Tryptophan with Coenzyme B-6, 120 Tablets, Source NaturalsSource Naturals L Tryptophan with Coenzyme B 6 Mood, Relaxation, Sleep. 500 mg Tablet. The essential amino acid L tryptophan helps support relaxation, restful sleep, and a positive outlook. It plays a part in the synthesis of both melatonin and serotonin, hormones involved with mood and stress response. This tryptophan includes the activated coenzyme form of vitamin B 6, called P 5 P, that is required to convert tryptophan to serotonin. L Tryptophan