N-acetyl cysteine (NAC)

N-acetyl cysteine (NAC) is the N-acetyl derivative of the protein amino acid L-cysteine, and is a precursor of the potent antioxidant glutathione. Glutathione however cannot cross the cell membrane, but NAC can, where it is converted to cysteine and then glutathione. As a result, NAC has an indirectly potent antioxidant activity, and is used to regenerate hepatic stores of glutathione that scavenge free radicals.