L-Cysteine Powder 100gm from Source NaturalsL Cysteine Mono HCI Powder L Cysteine is a sulfur containing amino acid that is converted in the body to N acetyl cysteine, a potent antioxidant. Cysteine is also a part of the reduced glutathione molecule, which plays an important role in the liver's detoxification pathways. Glutathione binds and conjugates toxins, promoting their excretion. Supplement Facts Serving Size: 1 4 teaspoon Amount %DV Cysteine (as L Cysteine monohydrochloride monohydrate)