Tag: Acetylated glutathione (oral bioavailability variant)

S-Acetyl-L-glutathione (SAG) is the S-acyl thioester of reduced glutathione (GSH) in which a single acetyl group is conjugated to the sulfhydryl moiety of the cysteine residue, shielding it from oxidation and enzymatic degradation during gastrointestinal transit and systemic circulation. The modification addresses the central pharmacokinetic limitation of oral GSH supplementation: native reduced glutathione is rapidly hydrolyzed by gamma-glutamyltransferase and dipeptidases in the intestinal lumen and brush border, resulting in less than 1 percent systemic bioavailability of the intact tripeptide after oral dosing in humans. By masking the reactive thiol as a thioester, SAG transits the gut mucosa substantially intact, permeates cell membranes by passive diffusion, and is deacetylated intracellularly by cytoplasmic thioesterases to regenerate free reduced glutathione, thereby replenishing the intracellular GSH pool without dependence on de novo synthesis from precursor amino acids.

The compound was first described in the medicinal chemistry literature as a glutathione S-acyl derivative in the 1970s, with early characterization of its sensitivity to human liver esterases. It entered the nutraceutical research field in the 2000s as a candidate oral glutathione delivery vehicle and has since been the subject of a single-center, single-dose, randomized, open-label, cross-over pharmacokinetic trial in 18 healthy volunteers (Fanelli et al., 2018), multiple preclinical studies in hepatoprotection and oncology, and a comprehensive toxicological safety assessment including bacterial reverse mutation assay, in vitro micronucleus testing, acute oral toxicity, and 13-week repeated-dose oral toxicity studies. The pharmacokinetic trial demonstrated that SAG is rapidly deacetylated to GSH after oral administration, with no quantifiable SAG detected in plasma at any time point; plasma GSH concentrations after SAG administration exhibited higher maximum concentration (Cmax) and area under the curve (AUC) compared to an equimolar dose of a marketed reduced glutathione product, with mean relative bioavailability exceeding that of the reference formulation.

Preclinical pharmacology has demonstrated hepatoprotective activity against carbon tetrachloride-induced liver injury through restoration of superoxide dismutase activity, glutathione peroxidase activity, and mitochondrial function, with concurrent suppression of the TLR4/NF-kappaB inflammatory cascade and reduction of proinflammatory cytokines TNF-alpha, IL-6, IL-1beta, and MCP-1. In oncology research, SAG selectively induces apoptosis in human lymphoma cell lines (Daudi, Raji, Jurkat) through a paradoxical intracellular GSH depletion mechanism while sparing normal lymphocytes and resistant lymphoma lines (Hut-78), a selectivity that has positioned it as a research tool for mechanism-based apoptosis investigation. The compound is manufactured by selective S-acetylation of reduced glutathione, achievable in a single step with cobalt chloride catalysis in dimethylformamide-trifluoroacetic acid solvent at yields exceeding 90 percent, and is commercially available from multiple research-grade suppliers at purities exceeding 98 percent by HPLC. It is supplied as a white to off-white crystalline powder with a molecular weight of 349.36 g/mol (CAS 3054-47-5), melting point of approximately 202 to 208 degrees Celsius, and stability at ambient temperature in dry storage. This monograph reviews the chemistry, synthesis, pharmacology, pharmacokinetics, preclinical and clinical evidence, sourcing, handling, safety, and comparative assessment of SAG against five alternative glutathione-repletion strategies.