Glutathione (GSH): A Research Compound Overview

Reduced L-glutathione (GSH) is the tripeptide γ-L-glutamyl-L-cysteinyl-glycine. Its unusual feature is the first bond: glutamate is joined to cysteine through its side-chain (gamma) carboxyl group rather than the usual alpha position, which makes it resistant to most peptidases. It carries CAS number 70-18-8, the molecular formula C10H17N3O6S, and a molecular weight of 307.32 g/mol.

The reactive part is the free thiol (-SH) on cysteine. Two GSH molecules can join through those thiols into a disulfide, glutathione disulfide (GSSG, C20H32N6O12S2, 612.63 g/mol), which is a different compound at twice the mass.

In the laboratory, glutathione is a standard substrate and reagent in glutathione S-transferase (GST) and glutathione reductase enzyme assays, and a reference material for thiol/disulfide redox chemistry, where the GSH to GSSG ratio is often the quantity being measured.

It is also used as a redox-state reference in cell-culture work and as an analytical reference standard. These are in vitro research applications only, and no medical claims are made here.

Reduced glutathione oxidizes on exposure to air and moisture, and the process accelerates once it is in solution. As a lyophilized powder it is stored long-term at -20°C (-4°F), desiccated and protected from light, with original labeling retained so the batch stays traceable.

This overview does not cover preparation or use of any kind. That falls outside laboratory research reference use, and we do not provide that guidance.

For glutathione, a single purity number can hide the most important fact about the sample. GSSG is the main degradation product of GSH, and it can elute near the main peak in a chromatogram. A report that integrates the two together, or that does not distinguish them, can show a high purity for material that is partly oxidized.

A useful glutathione certificate therefore states the method, shows the chromatogram, and ideally separates reduced from oxidized glutathione. This is why a per-batch Certificate of Analysis, one tied to the exact lot you receive, is more useful than a generic brand-level document.

Before relying on any batch, confirm three things: purity (an HPLC percentage with the chromatogram shown), identity (a match to a glutathione reference standard by retention time or mass spectrometry), and a traceable lot number with a test date. If the supplier lets you look up that batch’s report, you can match the documentation to the vial in hand.

Read the chromatogram itself, not just the summary number: a second peak sitting right beside the main one is worth asking the lab about.

Is glutathione an approved drug? There is no FDA-approved glutathione drug product in the United States. Glutathione appears in dietary-supplement and compounding-pharmacy contexts, which are regulated differently and are not what is offered here: a laboratory reference standard supplied strictly for analytical and in vitro research. Nothing on this site is medical guidance.

Is glutathione legal in the US? Glutathione is not a scheduled substance under the Controlled Substances Act. It is lawfully supplied as a reference material for laboratory research, and for no other purpose; nothing on this site should be read as a claim otherwise.

Reduced (GSH) versus oxidized (GSSG)? They are two different molecules: GSSG is two GSH units joined by a disulfide bond, at twice the mass. Research-grade glutathione is sold as the reduced form, and how much of it remains reduced is the quality question that matters.

Why a lyophilized vial? Reduced glutathione is far less stable in solution. Reference material is quantified by mass and stability-characterised in lyophilized form, which is what a per-batch certificate can actually describe.