Jun 7, Watermelon is one of the richest sources of citrulline. antioxidant that is converted to another amino acid called arginine by special enzymes. Jul 21, Did you know that watermelon has more lycopene than raw tomatoes? citrulline and arginine supplements derived from watermelon extract. Aug 20, That's because watermelon is rich in an amino acid called L-citrulline, which the body converts to L-arginine, an essential amino acid that helps. Nutrient Search: Foods highest in Lysine, and lowest in Arginine in Fruits and Fruit Juices. Watermelon, raw Lysine: mg Arginine: mg. Nutrition. Mar;23(3) Watermelon consumption increases plasma arginine concentrations in adults. Collins JK(1), Wu G, Perkins-Veazie P, Spears K. Scientists know that when watermelon is consumed, citrulline is converted to arginine through certain enzymes. Arginine is an amino acid that.