L-citrulline, like L-arginine and L-ornithine, is a metabolite in the urea cycle and is involved in liver detoxification and vasodilation pathways. It is produced in the urea cycle when carbamoyl phosphate is converted to citrulline in the ornithine carbamoyltransferase reaction. When endogenous supplies of ornithine carbamoyltransferase are insufficient, supplemental L-citrulline has been shown to support ammonia incorporation and liver detoxification of ammonia. Free form amino acid, high purity, well tolerated.