What is L-Glutathione?
On record for this item: CAS 70-18-8, formula C10H17N3O6S, molecular weight 307.32, sequence gamma-Glu-Cys-Gly, three residues joined through an unusual gamma-glutamyl bond at the first position. What can be said is that glutathione is a small, highly water soluble thiol bearing peptide, that the free sulfhydryl group is its reactive centre, and that it exists in two interconverting forms, one with a free thiol and one in which two molecules are joined by a disulfide bond. This item is the reduced form.
Glutathione is one of the most studied small molecules in cell biology. The ratio of reduced to oxidised forms is a standard readout of cellular redox state, and the molecule serves as cofactor for the glutathione peroxidase and glutathione S-transferase families in detoxification chemistry described across eukaryotic model systems. Cell culture work uses it as a reductant and as a measured endpoint.
What is not settled is how well exogenous glutathione crosses cell membranes intact, since transport appears limited in many cell types and breakdown to amino acids followed by intracellular resynthesis is an alternative explanation.
Reconstitution & handling
The reduced form dissolves readily in sterile or bacteriostatic water, added slowly down the vial wall with gentle swirling. The solution is acidic, and buffering it toward neutral accelerates air oxidation of the thiol, so solutions are prepared immediately before use. Concentration is simple arithmetic, so 2 mL added to a 200 mg vial yields 100 mg per millilitre.
Storage & stability
The sealed powder is stored at -20 °C, protected from light and moisture, and warmed to room temperature before opening because it is hygroscopic. The dominant stability concern is oxidation of the free thiol to the disulfide form, which proceeds on contact with air and is catalysed by trace metal ions, so metal spatulas and metal ion buffers are avoided. Solutions are refrigerated at 2 to 8 °C for the shortest practical period and aliquoted for single use.
How it's tested
Lots are analysed by reversed phase HPLC at 214 and 220 nm, with the assay specified to resolve the reduced form from the oxidised disulfide form, since the ratio is what matters for a reductant. Free thiol content is determined by a dedicated thiol assay rather than inferred from chromatographic purity, identity is confirmed by mass spectrometry, and a lot-matched certificate is available.