Amino Acid. Conditionally Essential Amino Acid. Nitric Oxide Precursor. Non-GMO. Kosher. Pharmaceutical Grade. Quality GMP Assured. L-Arginine is a conditionally essential basic amino acid involved primarily in urea metabolism and excretion, as well as DNA synthesis and protein production. It is an important precursor of Nitric Oxide (NO) and thus plays a role in the dilation of blood vessels.