Now Foods, L-Citrulline, 750 mg, 180 CapsProduct Description Citrulline 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.* Natural color variation may occur in this product. Product Benefits Support Protein Metabolism*. A Dietary Supplement.