L-Glutathione (Reduced Form, GSH)
Also Known AsGSH · gamma-L-Glutamyl-L-cysteinyl-glycine · Reduced Glutathione
Endogenous tripeptide present in virtually all mammalian cells, first identified by Frederick Gowland Hopkins in 1921. The unusual gamma-peptide bond between glutamate and cysteine (via the gamma-carboxyl group rather than the alpha-carboxyl) confers resistance to normal peptidase cleavage. It is the most abundant non-protein thiol in cells, reaching millimolar concentrations (1-10 mM) intracellularly.
gamma-Glu-Cys-GlyHow Glutathione Works
Glutathione Peroxidase Antioxidant System
Serves as the essential co-substrate for glutathione peroxidase (GPx) enzymes, which reduce hydrogen peroxide (H2O2) and lipid hydroperoxides to water and alcohols, respectively. Two molecules of GSH are oxidized to form glutathione disulfide (GSSG) per reduction reaction. The GSH/GSSG ratio is a primary indicator of cellular redox status.
Phase II Conjugation (Detoxification)
Acts as the nucleophilic co-substrate for glutathione S-transferase (GST) enzymes, which conjugate GSH to electrophilic xenobiotics, drug metabolites, and endogenous reactive compounds. GSH conjugates are exported via MRP transporters and further processed to mercapturic acids for renal excretion.
Thiol-Disulfide Redox Regulation
Maintains protein thiol homeostasis through glutaredoxin-mediated deglutathionylation reactions. Protein S-glutathionylation (reversible addition of GSH to protein cysteine residues) is a redox-signaling mechanism that regulates enzyme activity, transcription factor function, and ion channel conductance.
Ascorbate-Glutathione Cycle
GSH regenerates ascorbate (vitamin C) from its oxidized form (dehydroascorbate) via dehydroascorbate reductase. This cycle links the two major aqueous-phase antioxidant systems in cells and is particularly important in compartments with high oxidative flux.
Published Research
Oxidative Stress & Redox Biology
StrongGlutathione is the central molecule in cellular redox homeostasis. The GSH/GSSG ratio (normally >100:1 in cytosol) is the primary determinant of intracellular redox potential. Depletion below critical thresholds triggers redox-sensitive transcription factors (Nrf2, NF-kB, AP-1) and can initiate apoptotic cascades. Extensive literature across all disease models involving oxidative stress.
Hepatoprotection & Detoxification
StrongThe liver contains the highest concentration of GSH in the body (5-10 mM). Hepatic GSH is essential for Phase II drug metabolism, acetaminophen detoxification (NAPQI conjugation), and protection against alcohol-induced oxidative damage. N-acetylcysteine (NAC), the clinical antidote for acetaminophen poisoning, works by replenishing hepatic GSH stores.
Immune Function
ModerateLymphocytes and macrophages require adequate GSH for proliferation, cytokine production, and oxidative burst antimicrobial activity. GSH depletion impairs T-cell activation and NK cell cytotoxicity. Clinical studies in HIV, sepsis, and critical illness show correlation between GSH status and immune competence.
Neurodegenerative Disease
ModerateReduced GSH levels are documented in substantia nigra neurons in Parkinson's disease (one of the earliest detectable changes), in Alzheimer's disease brain tissue, and in ALS motor neurons. Whether GSH depletion is causative or consequential remains under investigation, but it precedes measurable neuronal loss in Parkinson's models.
Aging & GSH Decline
ModerateSystemic GSH levels decline with age across multiple tissues. The age-related decrease in GSH synthesis capacity (particularly gamma-glutamylcysteine ligase activity) correlates with increased oxidative damage markers. Glycine and cysteine supplementation studies in older adults show restoration of GSH synthesis and reduction of oxidative stress biomarkers.
Safety Profile
Glutathione is an endogenous molecule present at millimolar concentrations in all cells. Oral, sublingual, intravenous, and nebulized forms have been used in clinical research with an excellent safety profile. Intravenous GSH is used clinically in some countries for hepatoprotection. No significant adverse effects reported at supplemental doses. Oral bioavailability has historically been debated, but liposomal and sublingual delivery formats show improved absorption.
Handling & Storage
Reduced glutathione (GSH) is susceptible to oxidation. Store lyophilized powder at -20°C under inert atmosphere if possible. Reconstituted solutions should be used promptly as GSH auto-oxidizes in solution, especially at alkaline pH. For injection-grade material, reconstitute with bacteriostatic water and use at 2-8°C within 7-14 days. Solutions may be purged with nitrogen to reduce oxidation.
Peer-Reviewed Literature
- 1
- 2
Glutathione: overview of its protective roles, measurement, and biosynthesis
Forman HJ, Zhang H, Rinna A.
- 3
Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation
Sekhar RV, Patel SG, Guthikonda AP, et al.
- 4
Alterations in glutathione levels in Parkinson's disease and other neurodegenerative disorders affecting basal ganglia
Sian J, Dexter DT, Lees AJ, et al.
Glutathione FAQ
What is Glutathione?
Glutathione (GSH) is a tripeptide (gamma-Glu-Cys-Gly) present in virtually all mammalian cells at millimolar concentrations. It is the body's most abundant non-protein antioxidant and plays central roles in redox homeostasis, detoxification (Phase II conjugation), immune function, and protein thiol maintenance.
Why is the glutathione bond structure unusual?
Glutathione contains an unusual gamma-peptide bond: the glutamate residue is linked to cysteine through its gamma-carboxyl group rather than the standard alpha-carboxyl. This gamma-linkage makes GSH resistant to cleavage by standard cellular peptidases, contributing to its stability as an intracellular redox buffer.
What is the GSH/GSSG ratio and why does it matter?
The ratio of reduced glutathione (GSH) to oxidized glutathione disulfide (GSSG) is the primary indicator of intracellular redox status. A healthy cytosolic ratio exceeds 100:1. When oxidative stress depletes GSH faster than it is regenerated (by glutathione reductase using NADPH), the ratio drops, triggering redox-sensitive signaling cascades and potentially apoptosis.
How is Glutathione related to NAC (N-Acetylcysteine)?
NAC is a cysteine prodrug — it provides the rate-limiting amino acid (cysteine) for GSH biosynthesis. The clinical use of NAC as the antidote for acetaminophen overdose works by replenishing hepatic GSH stores needed to conjugate the toxic metabolite NAPQI. NAC supports GSH indirectly; glutathione provides the final molecule directly.
How should injectable Glutathione be stored?
Reduced glutathione auto-oxidizes in solution. Store lyophilized powder at -20°C. Once reconstituted, refrigerate at 2-8°C and use within 7-14 days. Nitrogen-purged vials extend solution stability. Keep pH near neutral — GSH oxidation accelerates at alkaline pH.
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All compounds 99%+ purity, verified by Janoshik Analytical. GMP-manufactured lyophilized powder.
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Disclaimer: This monograph is provided for educational and research purposes only. G26x Peptides products are sold exclusively as research chemicals. They are not intended for human consumption, therapeutic use, or as dietary supplements. All research should be conducted in compliance with applicable laws and institutional review board protocols. Information presented here is sourced from published peer-reviewed literature and does not constitute medical advice.