Glutathione: A Research Guide

Proxiva Compliance DeskResearch-use standards and labelling

Glutathione sits awkwardly in a peptide catalogue. It is technically a peptide — three residues joined by amide bonds — but it behaves in almost every practical respect more like a small molecule, and the vial sizes reflect that. This page covers what is actually being supplied, why the oxidation state is the specification that matters, and how the arithmetic compares against the rest of the catalogue.

What is glutathione, structurally?

A tripeptide of glutamate, cysteine and glycine. The cysteine residue carries a thiol group, and that thiol is the chemically active part — it is what allows the molecule to participate in redox reactions, and it is also what makes the molecule vulnerable to oxidation during handling.

Because it occurs endogenously, glutathione differs from most of the catalogue in an important way: it is not a designed analogue and it carries no stabilising modification. Compounds like Selank – 10mg and Semax – 10mg exist because their parent fragments clear too fast to be usable, and both carry an added proline-glycine-proline tail for that reason. Glutathione carries nothing analogous.

Why does the oxidation state matter more than purity?

Because there are two forms and only one is the functional species. Reduced glutathione (GSH) carries the free thiol. Oxidised glutathione (GSSG) is two glutathione molecules joined at that thiol — a disulfide dimer. They are different molecules with different behaviour, and material can drift from one to the other on exposure to air.

A certificate reporting “glutathione, 99% pure” has not answered the question that matters, because both forms are glutathione. The field to look for is the reduced fraction or an explicit GSH/GSSG determination. In practice this is the single most commonly omitted specification in this category, and it is more consequential than a percentage point of purity either way.

How does the cost compare to the rest of the catalogue?

It is not close. At $70 for 1500mg, glutathione runs $0.047 per milligram. For comparison, KPV – 10mg is $5.00/mg, Semax – 10mg is $5.00/mg, and TB-500 is $13.00–$15.00/mg.

That gap is a synthesis story, not a quality story. A three-residue peptide of common amino acids with no unusual modification is among the easiest things in this catalogue to make, and it is made at scale for other markets. Difficulty and scale set price here far more than anything about the molecule's usefulness.

What does the vial size change about handling?

Everything about the reconstitution arithmetic. A 10mg peptide vial reconstituted with 2mL gives 5mg/mL. A 1500mg vial reconstituted with the same 2mL gives 750mg/mL, which is a different order of problem — solubility becomes a real constraint rather than a formality, and the volumes involved are larger throughout.

The general handling rules still apply and matter more, not less, because of the thiol. Bring the vial to room temperature before piercing the stopper. Add Bacteriostatic Water down the wall rather than onto the cake. Swirl, do not shake. Keep the reconstituted vial cold and dark, and size the volume to the pace of consumption rather than filling it because the vial is large.

Air exposure is the specific risk here that other compounds do not share. Every puncture admits some air, and air is what converts the reduced form to the oxidised one. That is a direct argument for fewer, larger withdrawals rather than many small ones, and for a preservative-containing diluent so the working period is not additionally limited.

What should a certificate report?

Four things, in descending order of how often they are missing. The reduced fraction or an explicit GSH/GSSG split, which is the specification. Mass confirmation, because a three-residue molecule is small enough that identity should be unambiguous. Fill quantity, which at 1500mg is a larger absolute exposure than on a 10mg vial. And the method named rather than implied — a bare percentage with no assay stated is a claim, not a measurement.

Every batch sold here publishes its certificate on the test results page. The reduced-fraction question is the one to take to it.

What separates suppliers on a page like this

Composition and price are easy to publish and easy to copy. Documentation is neither. The axis on which suppliers in this market genuinely differ is what their certificate reports and whether it is published per batch rather than as a specimen. A specimen certificate demonstrates that a laboratory once tested something; a per-batch certificate tells you about the vial in your hand.

The fields worth checking, in rough order of how often they are missing: quantity per component for any blend, the analytical method named rather than implied, the testing laboratory identified, an endotoxin determination, and a date that corresponds to the batch rather than to the listing. Every batch sold here publishes its certificate on the test results page.

Two further notes on handling that apply to every compound referenced above. Lyophilised material ships dry and tolerates ambient transit; long-term storage is cold and dark. Bring a vial to room temperature before piercing the stopper, because solvent entering a cold vial invites condensation. Reconstitute with Bacteriostatic Water where more than one withdrawal is planned — the preservative is the entire reason to prefer it over sterile water — adding solvent down the wall rather than onto the cake, and swirling rather than shaking.

Why a blend name is not a specification

Almost every named preparation in this market — Wolverine, Glow, Klow and the rest — originated in forum usage rather than in any standards body. Nobody registered the name, nobody defined it, and no authority polices it. The practical consequence is that two suppliers can both list a product under the same name and ship vials that differ by a factor of two or more in total mass and in the ratio between components.

This is why composition published elsewhere for these names frequently describes well under half the totals quoted here, and it is why comparing two vendors on price alone produces a meaningless answer. A cheaper vial carrying the same name may simply contain less. The only comparison that means anything is milligrams of each named component against price, taken from each supplier's own published composition — and where a supplier does not publish per-component quantities, there is no comparison to make.

The same logic applies to any review or ranking of these products that does not state composition. A page comparing five vendors' versions of a named blend without listing what is in each one is comparing labels, not materials.

Reading a certificate without taking it on trust

Most certificates in this market are genuine and most are also thinner than they appear. Four habits separate a document that means something from one that merely exists. First, check that the batch or lot number on the certificate matches the number on the vial — a certificate that names no batch is a specimen, and a specimen tells you a laboratory once tested something. Second, check the date: a certificate predating the batch it purports to describe is a filing error at best. Third, read what was actually measured. “Purity >99%” by an unnamed method is a claim; “99.2% by RP-HPLC at 214nm” is a measurement. Fourth, look for what is absent — mass confirmation, endotoxin, and for any metal-containing complex the metal determination itself.

None of this requires analytical training. It requires reading the document as a record rather than as a reassurance, and noticing which fields are populated. A supplier publishing per-batch certificates with named methods is making a checkable commitment; one publishing a single undated specimen is not.

What this page does not claim

Nothing here describes an intended use in humans, and no outcome of any kind is asserted. The material is supplied for in-vitro laboratory and research use only. Where a mechanism is described it is described as reported in the literature for that compound, and the searches below return that literature directly — including whatever currently contradicts the framing above. Proxiva does not curate those results.

Where to read the primary literature

Proxiva does not summarise findings on behalf of a researcher. These are live searches against the two public registries, not curated citations — they return whatever is currently indexed, including results that contradict the framing above.

• PubMed: glutathione · ClinicalTrials.gov
• PubMed: reduced glutathione GSH · ClinicalTrials.gov
• PubMed: cellular redox · ClinicalTrials.gov
• PubMed: tripeptide antioxidant · ClinicalTrials.gov

Frequently asked questions

All materials listed are supplied strictly for in-vitro laboratory and research use. They are not drugs, foods or cosmetics, are not for human or veterinary use, and nothing on this page describes an intended use in humans. Figures quoted are catalogue list prices at the time of writing and change without notice.