Now Foods L-Citrulline, Pure PowderCitrulline is a non essential amino acid that is an important intermediate in the urea cycle, functioning along with other amino acids to rid the body of ammonia, a byproduct of protein metabolism.* Citrulline also plays an important role in the healing process and in the maintenance of a healthy immune system.*This product is sold by weight not volume. Natural color variation may occur in this product.