Glutathione (γ-L-glutamyl-L-cysteinylglycine, GSH) is a naturally occurring tripeptide composed of three amino acids: glutamine, cysteine, and glycine. It is synthesized intracellularly in nearly every cell of the human body and serves as the most abundant low-molecular-weight thiol antioxidant in living tissue.

Glutathione exists in two primary states: reduced (GSH), the active antioxidant form, and oxidized (GSSG), formed after neutralizing a free radical. The GSH/GSSG ratio is a key biomarker of cellular oxidative status, with higher GSH/GSSG ratios associated with healthier cellular environments.

In research, glutathione has been studied extensively for its central role in phase II liver detoxification, neutralization of reactive oxygen species, regeneration of other antioxidants including vitamin C and vitamin E, and conjugation of xenobiotics for elimination. Glutathione levels naturally decline with age, oxidative stress, and chronic disease, making it a peptide of significant interest in research on aging, hepatic function, and cellular resilience.”