L–Citrulline is an amino acid that has been found to play an important role in nitric oxide (NO) 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.
The pharmacokinetic advantage of L-Citrulline is that it is not subject to any elimination by the liver prior to entering the bloodstream. Conversely, L-Arginine is subject to extensive elimination by the gut wall and liver. (26)
The majority of L-Citrulline is converted to L-Arginine in the kidney. (3)
Once in circulation, L-Arginine is readily converted into L-Citrulline and nitric oxide, which in turn serves as an L-Arginine precursor (see figure below). (10)