What Does Arginine + Ornithine Do? Jarrow Formulas Arginine + Ornithine promotes ammonia detoxification, a performance-reducing end product of protein metabolism. Arginine is a precursor to ornithine, which can be converted back to arginine in the body. L-Arginine, a semi-essential amino acid, plays a central role in the urea cycle and synthesis of nitric oxide. Arginine is used to synthesize creatine, an important source of energy in skeletal muscle and the brain.