L-Citrulline in the HealthVit L-Citrulline Malate Powder is an amino acid that has been found to play an important role in nitric oxide, metabolism and regulation. L-Citrulline is converted to L-Arginine in the body, leading to increases in both L-Arginine and nitric oxide. Increased production of nitric oxide promotes vascular dilation, which helps support normal oxygen and blood circulation throughout the body. Roles of citrulline in the body are - Influences on blood vessels: Actions via nitric oxide production, vasodilation, blood flow acceleration. Ammonia detoxification: Action as a component of the L-ornithine cycle. Antioxidant effect: An active oxygen radical scavenger (potent quencher of hydroxyl radical).