Non-GMO A Dietary Supplement Amino Acids Family Owned Since 1968 GMP Quality AssuredAmino Acid Conditionally Essential Amino Acid Nitric Oxide PrecursorL-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.