L-GLUTATHIONE

Overview and Mechanism of Action

L-Glutathione (GSH) is a tripeptide composed of three amino acids: L-glutamic acid, L-cysteine, and glycine, assembled in the non-standard gamma-glutamyl linkage (γ-Glu-Cys-Gly) that distinguishes it from protease-susceptible standard peptide bonds and is critical to its biological stability. It is the most abundant non-protein thiol in mammalian cells, with intracellular concentrations in the millimolar range (typically 1–10 mM) in tissues such as the liver, lens of the eye, and erythrocytes. As the principal intracellular antioxidant, glutathione operates through multiple biochemical mechanisms that collectively defend cells against oxidative and nitrosative stress.

The primary redox mechanism involves the thiol (-SH) group of the cysteine residue, which is readily oxidized to form glutathione disulfide (GSSG) upon reaction with reactive oxygen species (ROS) including superoxide radicals, hydrogen peroxide, and lipid hydroperoxides. GSSG is subsequently reduced back to two molecules of GSH by glutathione reductase (GR) using NADPH as the reducing cofactor — a cycle that provides a continuously renewable antioxidant pool. Beyond direct radical scavenging, glutathione serves as the essential cofactor for glutathione peroxidases (GPx), a family of selenocysteine-containing enzymes that catalyze the reduction of hydrogen peroxide and lipid peroxides using GSH as the electron donor. Glutathione S-transferases (GSTs) conjugate GSH to electrophilic xenobiotics, environmental toxicants, and endogenous reactive metabolites, tagging them for membrane transport and excretion via the mercapturic acid pathway — a central mechanism of cellular detoxification.

Glutathione also maintains protein thiols in their reduced state via thiol-disulfide exchange reactions (a process termed glutathionylation and de-glutathionylation), regulates apoptosis through its influence on caspase activity and mitochondrial membrane potential, participates in the transport of cysteine across the blood-brain barrier as cysteinylglycine, and is a cofactor in prostaglandin synthesis and leukotriene metabolism. Its role in immune function includes the maintenance of T lymphocyte proliferative capacity and the regulation of cytokine production, with GSH depletion associated with impaired lymphocyte responses in multiple research models.

Research History and Development

Glutathione was first isolated from yeast by Frederick Gowland Hopkins in 1921 and subsequently characterized as a tripeptide in the 1930s. Its role in cellular redox homeostasis was progressively elucidated through the twentieth century, with major contributions from research groups investigating the enzyme systems responsible for its synthesis (gamma-glutamylcysteine synthetase and glutathione synthetase), recycling (glutathione reductase), and utilization (glutathione peroxidases and S-transferases). Albert Meister's laboratory at Cornell University made foundational contributions to understanding the gamma-glutamyl cycle and the metabolic regulation of GSH biosynthesis.

Research interest in exogenous glutathione administration expanded as the compound's roles in aging, neurodegeneration, cancer biology, immune function, and xenobiotic detoxification became clearer. Studies examining GSH depletion in conditions including Parkinson's disease, cystic fibrosis, HIV infection, and cancer chemotherapy toxicity have generated substantial investigational interest. A key area of ongoing research concerns bioavailability: oral glutathione was historically considered poorly bioavailable due to gastrointestinal hydrolysis, but more recent studies employing liposomal formulations, S-acetyl glutathione precursors, and specialized oral delivery systems have challenged this assumption. Intravenous, intranasal, and nebulized administration routes have been employed in clinical research to circumvent first-pass degradation.

Typical Research Parameters

In cell culture research, glutathione depletion is commonly induced with buthionine sulfoximine (BSO), a gamma-glutamylcysteine synthetase inhibitor, to create GSH-deficient model systems before examining the consequences for oxidative stress, apoptosis, or xenobiotic metabolism. Exogenous GSH supplementation in vitro is typically performed at concentrations of 0.1–5 mM, depending on the cell type and endpoint. Intracellular GSH quantification employs spectrophotometric assays (Ellman's reagent, DTNB-based) or fluorescent probes such as monobromobimane. In animal models, subcutaneous, intraperitoneal, or intravenous administration of GSH has been studied at doses ranging from 50 to 500 mg/kg. For research use only.

Storage Requirements

L-Glutathione is susceptible to oxidation of its cysteine thiol, which is the primary stability concern during storage and handling. Lyophilized powder should be stored at -20°C under inert gas (nitrogen or argon) or in a well-sealed, desiccated container to minimize oxidative exposure. Aqueous solutions are substantially less stable than the dry powder and should be prepared fresh immediately before use, or alternatively stored at -80°C under inert atmosphere in small single-use aliquots. Acidic pH (4–5) improves solution stability. Contact with metal ions (particularly copper and iron), which catalyze thiol oxidation, should be avoided. Use metal-chelated (EDTA-supplemented) buffers where possible.

Safety Notes and Research Considerations

L-Glutathione has an excellent safety profile in published research across a wide range of administration routes and doses. Its endogenous nature and ubiquitous cellular distribution mean that exogenous supplementation is generally well tolerated in animal models. Researchers should verify the reduced (GSH) versus oxidized (GSSG) content of research preparations by HPLC or Ellman's assay before use, as poorly stored material may be substantially oxidized and thus of reduced biological relevance. In cytotoxicity assays, the reducing capacity of GSH can interfere with certain colorimetric viability reagents (e.g., MTT, resazurin) via direct chemical reduction; appropriate controls are essential. This material is for research purposes only.

Synthesis Regulation in the Published Literature

Two reviews anchor the biochemistry. Glutathione is synthesized from glutamate, cysteine, and glycine by two cytosolic enzymes, glutamate cysteine ligase (GCL, composed of catalytic GCLC and modifier GCLM subunits) and glutathione synthetase; GCL activity, cysteine availability, and GSH feedback inhibition are the primary regulators. GCLC, GCLM, and GS are regulated at multiple levels, often in coordination, by transcription factors including Nrf2 acting through the antioxidant response element, AP-1, and NF-κB. Animal and human studies show that adequate protein nutrition is required to maintain GSH homeostasis, and that cystine, methionine, N-acetylcysteine, and L-2-oxothiazolidine-4-carboxylate are effective cysteine precursors for tissue GSH synthesis. This is the reason many research designs manipulate GSH indirectly through precursor supply or BSO-mediated GCL inhibition rather than by adding GSH itself, and why exogenous GSH experiments need to account for extracellular degradation by γ-glutamyl transpeptidase before the tripeptide reaches the cytosol.

Live Market Data on Peptides.SO (listing data on file as of 13 September 2026)

Peptides.SO tracks 46 listings for L-glutathione from 41 suppliers. Prices run from $0.80 to $332.13, with a median of $72.96; the middle half of listings fall between $41.99 and $84.63. The median list price across the 512 priced listings in the platform's anti-aging category is $79.99, so the typical glutathione listing sits about 9% below the category midpoint. Five listings currently show a discounted price, averaging a 29% markdown. The wide range is driven almost entirely by vial mass: glutathione is sold in far larger quantities than most research peptides (1,500 mg vials are common), so per-mg pricing is the only meaningful basis for comparison, and the sub-$1 entry is a per-mg quote rather than a vial price.

Because glutathione is a commodity biochemical as well as a research-peptide listing, the reduced-to-oxidized ratio matters as much as purity. No supplier on the platform currently has a testing score or a certificate-of-analysis link on file, so ask the vendor for an HPLC assay that resolves GSH from GSSG and for the free-thiol content by Ellman's reagent on the specific lot.

Frequently Asked Questions

Why do glutathione prices vary so much between suppliers? Vial sizes range from research-scale milligram quantities to multi-gram bulk lots. Compare on a per-mg basis using the supplier table on this page rather than on headline vial price.

What does "reduced" glutathione mean on a listing? It means the thiol form (GSH) rather than the disulfide (GSSG). Poorly stored material oxidizes, so a listing labeled "reduced" should still be verified by assay before use in a redox experiment.

Is L-glutathione the same as glutathione? Yes. The L- prefix specifies the natural stereochemistry of the constituent amino acids; all biologically relevant glutathione is the L-form.

Does exogenous glutathione enter cells intact? Generally not efficiently. It is largely broken down extracellularly by γ-glutamyl transpeptidase into constituent amino acids that are then used for intracellular resynthesis, which is why precursor strategies are common in the literature.

Related Pages on Peptides.SO

Background reading: the glutathione (GSH) antioxidant tripeptide research profile and the glutathione reconstitution research guide. Related redox and NAD+ pages: NAD+ price comparison and the NAD+ cellular energy overview. Use the reconstitution calculator for molar conversions and the CoA guide when evaluating a vendor's GSH/GSSG assay.

Cited Research

Wu G et al.. Glutathione metabolism and its implications for health. J Nutr. 2004. PubMed 14988435

Lu SC. Glutathione synthesis. Biochim Biophys Acta. 2013. PubMed 22995213

Lu SC. Regulation of glutathione synthesis. Mol Aspects Med. 2009. PubMed 18601945

For laboratory research use only. Not for human or veterinary use, diagnosis, treatment, cure, or prevention of any disease. THIS PRODUCT IS NOT FOR HUMAN CONSUMPTION.