L-Phenylalanine 500 mg, 50 Tablets - Source Naturals.Source Naturals LPhenylalanine, 500 mg, 50 Tablets, is a dietary supplement that provides 500 mg of Lphenylalanine per tablet. Lphenylalanine is an essential amino acid, meaning it must be obtained through the diet as the body cannot produce it. This amino acid is a precursor to tyrosine, which is subsequently converted into Ldopa. Ldopa then converts into norepinephrine, a neurotransmitter and adrenal hormone. Additionally, Lphenylalanine is a direct