Glutathione (GSH): Form, Reconstitution and Lab Handling

Physical form and specification

Reduced glutathione (GSH) ships as a white lyophilized (freeze-dried) powder in a sealed glass vial, packaged at 1500 mg per vial, ≥98–99% purity by HPLC. It is not a peptide-hormone analog but an endogenous antioxidant tripeptide, γ-L-glutamyl-L-cysteinyl-glycine (MW 307.32), and the free thiol (–SH) on its cysteine residue is the redox-active group that governs how it behaves once dissolved.

Reconstitution chemistry

The lyophilizate dissolves readily in water. Bacteriostatic water (0.9% benzyl alcohol) or sterile water for injection is the common reconstitution solvent for research stocks; the benzyl alcohol limits microbial growth in a multi-draw vial. Introduce the diluent slowly down the vial wall and swirl gently until clear — glutathione is highly soluble, so no vigorous mixing is needed. The controlling variable here is not foaming but oxidation: the reduced thiol converts to the disulfide GSSG in air, fastest at neutral-to-alkaline pH and in the presence of transition-metal ions (copper, iron). Solutions are more stable at weakly acidic pH, so prepare the stock fresh and use it promptly. Concentration is set by the diluent volume (mass in the vial ÷ mL added). Sterile water or a defined buffer can be substituted where a preservative-free matrix is required, at the cost of no bacteriostatic protection.

Storage and stability

The sealed lyophilized vial is the stable form: keep it cold and protected from light and moisture; the dry powder tolerates months, and a freezer suits long-term holds. Once reconstituted, the reduced form oxidizes readily, so its clock starts immediately: keep the solution at 2–8 °C, shielded from light, and use it promptly rather than storing it. Avoid repeated freeze-thaw, which accelerates oxidation and aggregation. Discard any solution that turns cloudy, yellowed, or shows particulates — discoloration signals oxidation to GSSG.

Lab handling

Let a cold vial equilibrate to room temperature before opening to avoid condensation onto the powder. To slow oxidation of research stocks, work at weakly acidic pH and add a metal chelator (EDTA), and minimize headspace and air exposure once the vial is open. Record the lot number and reconstitution date on the vial.

Research context

Glutathione is the most abundant intracellular non-protein thiol and the cell's dominant low-molecular-weight redox buffer; the GSH/GSSG ratio is a standard readout of oxidative status. It is widely used in vitro and in animal models to study oxidative stress, xenobiotic detoxification via glutathione-S-transferase conjugation, and thiol-based redox signaling, and as a reference antioxidant in comparative assays. This material is supplied for laboratory research use only.