L-Tryptophan (Tryptophan) is an essential amino acid that is the precursor of serotonin, melatonin, and vitamin B3[1].
References:
[1]. Slominski A, et al. Conversion of L-tryptophan to serotonin and melatonin in human melanoma cells. FEBS Lett. 2002 Jan 30;511(1-3):102-6.
















