L-Citrulline Powder 99% is commonly used to promote overall athletic performance and especially for endurance exercise or intense physical activity. The amino acid was initially extracted from watermelon (“Citrullus”) and that is how the compound got the name. While it isn’t an amino acid directly involved in building proteins, it does increase protein synthesis by stimulating a crucial signaling pathway that is involved in muscle building. In the body some of the L-Citrulline is converted into L-Arginine and further on into nitric oxide. The latter is a vasodilator that widens veins and arteries. This improves blood flow and reduces blood pressure, which can be helpful for preventing the occurrence of certain diseases.