L-Citrulline 750 mg, 180 Capsules, NOW FoodsNOW Citrulline 750 mg Cardiovascular Health. Promotes Nitric Oxide Production. Supports Vascular Blood Flow. 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 for Arginine production, which inturn, can be