DL Phenylalanine is not a vitamin, it is an amino acid. Amino acids are the building blocks of protein. This amino acid, when taken as a supplement, can reduce pain, increase alertness, improve mood and may help Parkinson's disease. My source for this info is 'Prescription for Nutritional Healing" by Phyllis Balch.
Phenylalanine is a bulky hydrophobic amino acid, which can be incorporated into proteins like any other amino acid. It can also be converted to tyrosine which is a precursor of dopamine and adrenalin.
Phenylalanine (abbreviated as Phe or F)[1] is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5, which is found naturally in Cytoplasm.
The chemical formula of phenylalanine is C6H5CH2CH(NH2)COOH; phenylalanine is an essential aminoacid.