L-Citrulline Pure Powder, 4 oz, NOW FoodsNOW Foods L Citrulline Powder Cardiovascular Health. 100% Pure Powder. Promotes Nitric Oxide Production. Supports Vascular Blood Flow. Vegetarian Product. Citrulline is a non essential amino acid that is an important intermediate in the urea cycle, functioning along with Arginine and Ornithine to rid the body of ammonia, a byproduct of protein metabolism. Because Citrulline is a precursor of Arginine, it provides a readily available source material