here some info
L-Phenylalanine is an essential, nine-carbon amino acid and is a precursor to the amino acid tyrosine. Because tyrosine is necessary for the synthesis of proteins and the production of the neurotransmitters dopamine and norepinephrine, phenylalanine is an extremely important nutrient that must be obtained through the diet or supplementation. As the building blocks of protein, amino acids are vital to health. Next to water, amino acids in the form of proteins make up the greatest portion of our body weight. They comprise tendons, muscles and ligaments; organs and glands; hair and nails; important bodily fluids, and are a necessary part of every cell in the body.
There are over 20 amino acids, separated into two categories - essential and non-essential. Essential amino acids are those that cannot be manufactured by your body, hence, it is essential that you obtain them from your diet. Non-essential amino acids can be manufactured by your body. L-Phenylalanine is an essential amino acid. Amino acids are not only absolutely integral to life, but they can have a profound impact upon how clearly we think and how well we feel.