Metabolism of Citrulline: You can obtain Citrulline from food, especially watermelons, and it can be also manufactured from ornithine, in the body’s urea cycle. This cycle helps rid your body of ammonia, a waste product of protein digestion. After your digestive system metabolizes citrulline malate into citrulline, enzymes in your liver cells convert it into arginine, then into nitric oxide...