Webb Nutrition® NAC capsules have been manufactured to the highest standards they come in a handy resealable foil pouch for hygiene and freshness. Absolutely no additives, just pure N Acetyl L Cysteine powder encapsulated! N-Acetyl L-Cysteine (NAC), is a derivative of the amino acid L-cysteine, a precursor in the formation of glutathione. Glutathione is one of the body’s most important antioxidants.