Glutathione: Identity, Redox Chemistry and Documentation

What glutathione is

Glutathione is a tripeptide made of glutamate, cysteine and glycine. Its molecular weight is about 307 Da. It is unusual among peptides because the first bond is not a standard peptide bond: the glutamate is joined through its side-chain carboxyl group, giving the gamma-glutamyl linkage written as gamma-Glu-Cys-Gly. That linkage is why ordinary peptidases do not break it down, and why cells need a dedicated enzyme to recycle it.

Is glutathione a peptide? Yes, by structure. It is also an endogenous metabolite found in every cell in the body, made on demand by two enzymes rather than on a ribosome. Both facts are true at once, and the second is why it is studied as a redox molecule rather than as a signalling peptide.

Reduced and oxidised forms

The chemistry that matters is at the cysteine thiol.

Inside a cell, the ratio of GSH to GSSG is used as a measure of redox state, and GSH acts as a substrate for glutathione peroxidases and glutathione S-transferases. These are the biochemical roles described in textbooks, and they are the reason research material is normally specified as the reduced form.

The thiol is also the stability problem. In solution, in air, GSH oxidises to GSSG over hours to days depending on pH, temperature and metal ions. Solid lyophilised material is far more stable, which is why research material is supplied as powder and why a certificate measured on the solid does not describe a solution made from it later.

What the research literature covers

The glutathione literature is enormous because it is a core metabolite, and most of it is about the molecule made inside cells, not about added material. Studies that add glutathione to a system fall into three groups.

• •Cell culture studies of oxidative stress models, where GSH or its precursors are added to the medium.
• •Animal studies of depletion and repletion.
• •Human studies, mostly of oral or intravenous pharmaceutical products, which concern those products and their formulations.

The search phrase "glutathione injection" refers to products administered in aesthetic clinics in several countries. In the UK such use is unlicensed. It has no connection to a research reagent, and this page makes no claim about it.

Analytical documentation

Glutathione is simple to characterise and awkward to keep characterised. Mass spectrometry confirms the expected mass for GSH. HPLC separates GSH from GSSG, so a purity figure for the reduced form should be read together with the method and the date, because the GSSG share rises with time once the vial is opened. A batch certificate for the material should show the method and the date, and how to read a peptide COA explains those fields. As with every material on this site, the certificate reports identity and purity of the sample tested and nothing about biological activity.

Scope and laboratory-use boundary

Materials sold on this site are supplied solely for non-clinical in-vitro laboratory research. They must not be ingested, injected, inhaled, applied or otherwise administered to a human or animal.

We do not provide dosing, routes of administration, treatment guidance, cosmetic-use guidance or in-vivo protocols. Preparation, storage and handling must follow a validated institutional SOP, the material documentation and an appropriate risk assessment.