Antioxidant Amino Acid – N-Acetyl-L-Cysteine (NAC) is an antioxidant amino acid that contributes cysteine to the antioxidant glutathione, which is a tripeptide of cysteine, glycine and glutamate. Cellular Health & Liver Function Jarrow Formulas N-A-C supports the detoxification function of the liver and supports the immune system, as well as glutathione synthesis.