S-Acetyl-L-Glutathione Encyclopedia — Scientific Background

What Is S-Acetyl-L-Glutathione?

S-Acetyl-L-glutathione (CAS 3054-47-5), also known as S-acetylglutathione or SAG, is an acetylated tripeptide composed of cysteine, glutamic acid, and glycine, with the molecular formula C₁₂H₁₉N₃O₇S and a molecular weight of 349.36 g/mol. It is an S-acylglutathione in which the S-acyl group is specified as acetyl, and it has demonstrated roles as an anti-HSV-1 agent and apoptosis inducer. SAG is the S-acetylated bioavailable form of L-glutathione (L-GSH) in its reduced form, obtained through chemical synthesis, and is presented as a white or almost white crystalline powder.

The S-Acetyl Advantage Over Native Glutathione

Native glutathione (GSH) fails in oral bioavailability due to gastrointestinal degradation. It is not well absorbed from the gut, has a short half-life in blood plasma, and is not efficiently taken up by cells. S-Acetyl-L-glutathione solves this problem via acetylation of the cysteine thiol group, which protects the thiol moiety from enzymatic degradation and enables direct cellular uptake.

The critical difference between SAG and native GSH lies in the acetyl group attached to the sulfur atom. This acetyl group prevents SAG from being degraded by γ-glutamyl transpeptidase (γ-GT), the enzyme responsible for the rapid breakdown of GSH in the gastrointestinal tract and bloodstream. Once inside the cell, cytosolic thioesterases remove the acetyl group, releasing the intact, bioactive GSH molecule.

Compared with glutathione and other glutathione derivatives, SAG exhibits better stability, faster onset of action, higher bioavailability, and superior safety. Oral administration of SAG has been shown to be more effective in restoring intracellular glutathione levels compared to oral glutathione.

Mechanisms of Action

Intracellular GSH Restoration via Thioesterase-Mediated Conversion

The interaction of SAG with cellular enzymes is a two-step process: initial deacetylation by thioesterases followed by the participation of the liberated GSH in a multitude of enzymatic pathways. SAG is stable in blood and can be converted to glutathione by intracellular thioesterases. This mechanism allows SAG to bypass the enzymatic degradation that limits the bioavailability of native GSH, delivering the active glutathione molecule directly into cells.

Antioxidant Defense and Free Radical Scavenging

SAG has demonstrated antioxidant stress effects, free radical scavenging activity, and inhibition of ferroptosis. By restoring intracellular GSH levels, SAG supports the body‘s primary antioxidant defense system, protecting cells from oxidative damage caused by reactive oxygen species (ROS) and reactive nitrogen species (RNS).

Detoxification Pathways

GSH is a potent defense compound against oxidative stress and a key determinant of many other physiological functions. It acts as an antioxidant, a free radical scavenger, and a detoxifying agent. By replenishing intracellular GSH, SAG supports phase II detoxification pathways, including glutathione S-transferase (GST)-mediated conjugation of xenobiotics and carcinogens.

Skin Brightening and Anti-Aging

As a tyrosinase inhibitor, SAG reduces melanin production in cells caused by tyrosinase activity due to sun exposure, thereby achieving a whitening effect. By reducing oxidative stress and inflammatory responses, it helps to delay the skin aging process, making the skin firmer and more elastic. SAG can be recommended for use as an antioxidant, anti-aging, whitening, and skin conditioning agent in cosmetics.

Clinical Evidence

Performance Recovery in Athletes — Randomized Controlled Trial

A randomized, double-blind, crossover, repeated-measures clinical trial is evaluating S-Acetyl Glutathione (SAG) for performance recovery in soccer players. Participants will receive daily doses of 200 mg SAG, 500 mg SAG, or placebo, with the study designed to assess the impact of SAG supplementation on recovery markers following exercise. S-Acetyl Glutathione is a glutathione precursor with enhanced absorption kinetics due to chemical S-acetylation of the thiol group on the cysteinyl amino acid of GSH, and oral administration of SAG has been shown to be more effective in restoring intracellular glutathione levels compared to oral glutathione.

Safety and Tolerability — Preclinical Evidence

A comprehensive safety assessment of S-Acetyl Glutathione was conducted using in vitro bacterial reverse mutation assay, in vitro micronucleus test, acute oral toxicity study, and a repeated dose (13-week) toxicity study. The in vitro assays did not reveal any genotoxic or mutagenic activity. No mortality or morbidity resulted from the acute oral toxicity study (LD50 > 2000 mg/kg). Administration of SAG over 13 weeks was well tolerated and did not result in any neurobehavioral alterations or effects on locomotor activity, ophthalmology, hematology, coagulation, blood biochemistry, urinalysis, thyroid hormones, or the male reproductive system. The NOAEL was determined to be 1500 mg/kg/day, the highest dose tested, and the results support the safe use of SAG in foods or dietary supplements.

EFSA Novel Food Safety Opinion

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on S-acetyl glutathione (SAG) as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF consists of >97% (w/w) SAG. The information provided on the production process, composition, and specifications of the NF did not raise safety concerns. The NF is proposed to be used as a food supplement and as food for special medical purposes at a maximum dose of 300 mg NF/day, targeting the general population excluding individuals below 10 years of age and pregnant or lactating women. The Panel concluded that the NF is safe at the proposed conditions of use of 300 mg/day for adults, excluding pregnant and lactating women.

The Bioavailability Challenge

Despite its critical physiological functions, native glutathione presents significant bioavailability challenges. GSH is not well absorbed from the gut, has a short half-life in blood plasma, and is not efficiently taken up by cells. The primary reason for this poor bioavailability is the rapid enzymatic degradation of GSH by γ-glutamyl transpeptidase (γ-GT) in the gastrointestinal tract and bloodstream.

liposomal encapsulation of SAG provides an additional layer of protection beyond the acetyl modification itself. The phospholipid bilayer surrounds the SAG molecule, forming a protective shell that shields it from enzymatic degradation during digestive transit and facilitates efficient cellular delivery. This dual protection—chemical acetylation plus liposomal encapsulation—ensures maximum stability and bioavailability.

Liposomal S-Acetyl-L-Glutathione

Liposomal encapsulation of SAG provides a fundamentally different delivery mechanism from conventional forms. The phospholipid bilayer surrounds the SAG molecule, forming a protective shell that enhances stability, absorption, and cellular uptake. This delivery system:

• Provides an additional protective layer beyond the acetyl modification itself

• Shields SAG from enzymatic degradation during digestive transit

• Facilitates efficient cellular delivery via lipid-mediated pathways

• Supports sustained release for prolonged intracellular GSH restoration

• Enhances water dispersibility for use in aqueous formulations

The acetyl group on the sulfur atom enhances stability and bioavailability, making SAG a subject of interest in pharmaceutical and nutraceutical research. Liposomal encapsulation further optimizes this delivery system, ensuring that SAG reaches target cells intact and is efficiently converted to bioactive GSH by intracellular thioesterases.

Safety and Regulatory

S-Acetyl-L-glutathione has a well-established safety profile. Genotoxicity assays (Ames and micronucleus) were negative, acute oral LD50 exceeded 2000 mg/kg, and a 13-week repeated dose study established a NOAEL of 1500 mg/kg/day, the highest dose tested.

Regulatory status:

• European Union — EFSA has published a positive safety opinion on S-Acetyl Glutathione (SAG) as a novel food pursuant to Regulation (EU) 2015/2283. The NF is safe at the proposed conditions of use of 300 mg/day for adults, excluding pregnant and lactating women. For young and older adolescents, the Panel considers the NF safe at intake levels up to 190 and 269 mg/day, respectively.

• United States — S-Acetyl-L-glutathione is commercialized as a dietary supplement ingredient.

• Global Standards — SAG is available as a research chemical with purity ≥98% from major suppliers.

Testing protocols must adhere to international standards including USP, European Pharmacopoeia, and FAO/WHO Codex Alimentarius. Formulators should verify local regulatory requirements prior to market entry.

This product is intended for research, nutraceutical, and functional food applications. Not intended to diagnose, treat, cure, or prevent any disease.

569$/KG

459$/KG