What is the glutathione formula and molecular weight?

Reduced glutathione (GSH) is C10H17N3O6S, 307.33 g/mol, CAS 70-18-8. Oxidised glutathione (GSSG) is C20H32N6O12S2, 612.6 g/mol, CAS 27025-41-8.

What does glutathione do in cells?

It is the substrate glutathione peroxidases use to reduce hydrogen peroxide and lipid hydroperoxides, and glutathione S-transferases attach it to reactive compounds for removal. The GSH/GSSG ratio is a standard measure of a cell's redox state.

What is the difference between GSH and GSSG?

GSH is reduced glutathione, with a free cysteine thiol. GSSG is glutathione disulfide: two GSH molecules joined through their cysteines after oxidation. Glutathione reductase converts GSSG back to GSH using NADPH.

Is glutathione FDA-approved?

Not as a drug ingredient, although oxidised glutathione is one component of the approved eye-surgery solution BSS PLUS. It is a GRAS food ingredient and a dietary supplement in the US, and it is under evaluation in FDA's compounding category 1.

Does Clean Peptide sell glutathione?

No. This page is a reference summary. Our catalogue is research peptides with per-lot certificates.

Glutathione Peptide: Structure, Function & Research

Q: Is glutathione a peptide?

Chemically, yes: it is the tripeptide γ-glutamyl-cysteinyl-glycine. It is made by two enzymes rather than from a gene, its first bond is a γ-glutamyl bond that ordinary peptidases do not cut, and regulators list it simply as glutathione.

Glutathione (GSH) is a tripeptide, γ-L-glutamyl-L-cysteinyl-glycine, and the most abundant small thiol made in human cells. Its first link is unusual: glutamate joins cysteine through its side-chain γ-carboxyl, not the α-carboxyl of an ordinary peptide bond, and the cysteine’s –SH group does the chemical work. Clean Peptide does not stock glutathione; this page is a reference summary.

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Glutathione at a glance

Names	Glutathione, reduced glutathione, GSH, L-glutathione, γ-Glu-Cys-Gly
Structure	Tripeptide: γ-glutamyl–cysteine bond, then an ordinary cysteine–glycine peptide bond
Molecular formula	C₁₀H₁₇N₃O₆S
Molecular weight	307.33 g/mol
CAS number	70-18-8 (reduced, GSH); 27025-41-8 (oxidised, GSSG)
PubChem CID	124886
Oxidised form	Glutathione disulfide (GSSG): two GSH molecules joined by a disulfide bond, 612.6 g/mol
Made by	Every mammalian cell, in two enzyme steps; not encoded by a gene
In our catalogue	Not stocked

Sources: the FDA substance registry (GSRS UNII GAN16C9B8O), PubChem and CAS Common Chemistry.

Is glutathione a peptide?

Chemically, yes: it is three amino acids joined together, and ChEBI classes it as a tripeptide. It is not usually called a “peptide” in the sense research catalogues use the word, for three reasons. It is not made by ribosomes from a gene but assembled by two enzymes; its first bond is a γ-glutamyl bond that ordinary peptidases do not cut; and regulators and pharmacopoeias list it simply as glutathione. “Glutathione peptide” appears in only a dozen PubMed records, against more than 180,000 for glutathione. Glutathione synthesis. Lu SC. Biochimica et Biophysica Acta, 2013.

What glutathione does in cells

Inside cells glutathione is present at roughly 1–10 mM, highest in the liver, which also exports most of the glutathione found in plasma. It is made in the cytosol in two ATP-dependent steps: glutamate-cysteine ligase joins glutamate and cysteine, and glutathione synthetase adds glycine. Outside cells it is broken down by γ-glutamyl transpeptidase, the enzyme Orlowski and Meister placed at the centre of their 1970 “γ-glutamyl cycle”. Lu SC, 2013; The gamma-glutamyl cycle: a possible transport system for amino acids. Orlowski M, Meister A. PNAS, 1970.

Peroxide removal. Glutathione peroxidases use GSH to reduce hydrogen peroxide and lipid hydroperoxides, producing GSSG, which glutathione reductase turns back into GSH using NADPH. Mammals have eight glutathione peroxidases, five of them containing selenium; the selenium link was found in 1973. Glutathione peroxidases. Brigelius-Flohé R, Maiorino M. Biochimica et Biophysica Acta, 2013; Rotruck JT, et al. Science, 1973.
Conjugation. Glutathione S-transferases attach GSH to electrophilic compounds, from foreign chemicals to reactive by-products of the cell’s own metabolism, as a first step in their removal. Glutathione transferases. Hayes JD, et al. Annual Review of Pharmacology and Toxicology, 2005.
Redox balance. The ratio of reduced to oxidised glutathione is one of the standard measures of a cell’s redox state. Glutathione: overview of its protective roles, measurement, and biosynthesis. Forman HJ, et al. Molecular Aspects of Medicine, 2009.

Human studies of supplied glutathione

ClinicalTrials.gov lists more than 270 studies with glutathione as an intervention. A recurring question is how much of it survives to reach the blood, and the studies below are listed by what they measured.

Oral absorption (1992). Plasma glutathione, cysteine and glutamate were measured for 4.5 hours after one oral dose in 7 volunteers. The systemic availability of oral glutathione. Witschi A, et al. European Journal of Clinical Pharmacology, 1992.
Intravenous pharmacokinetics (1991). Volume of distribution, elimination and half-life after a single infusion in 10 volunteers. Aebi S, et al. European Journal of Clinical Investigation, 1991.
Six-month oral trial (2015). A randomised placebo-controlled trial in 54 adults measured glutathione in blood, red cells, plasma, lymphocytes and cheek cells over six months. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Richie JP Jr, et al. European Journal of Nutrition, 2015.
Liposomal and sublingual forms (2015, 2018). A pilot study of liposomal glutathione in 12 adults and a crossover comparison of oral, sublingual and N-acetylcysteine forms in 20 volunteers. Sinha R, et al., 2018; Schmitt B, et al., 2015.
Other settings. Small trials have tested intravenous and intranasal glutathione in Parkinson’s disease and oral glutathione in cystic fibrosis. Two systematic reviews of glutathione and skin colour judged the evidence inconclusive or of mixed quality. Mischley LK, et al., 2017; Bozic M, et al., 2020; Dilokthornsakul W, et al., 2019; Sarkar R, et al., 2025.

A 2026 systematic review concludes that low oral bioavailability, rapid breakdown and inconsistent results still limit the clinical use of supplied glutathione. Carnib BL, et al. Biomedicine & Pharmacotherapy, 2026.

Regulatory status

In the US, glutathione is not an FDA-approved drug ingredient, although oxidised glutathione is one component of the approved ophthalmic irrigating solution BSS PLUS. FDA accepted a GRAS notice for glutathione as a food ingredient in 2009, and it is sold as a dietary supplement. For pharmacy compounding it sits in FDA’s 503A category 1, under evaluation; at a 2022 advisory committee meeting FDA proposed not listing it and the committee voted 8–5 with one abstention in favour. FDA has also warned compounders, in 2019 and again on 27 August 2026, about adverse events linked to intravenous products made from supplement-grade glutathione. FDA alert, 2019; FDA alert, August 2026; FDA advisory committee minutes, June 2022. In Italy, injectable glutathione products are authorised nationally.