Glutathione

Glutathione (GSH) is the body's most abundant intracellular antioxidant, present in virtually every cell at millimolar concentrations. Its mechanism centres on the reactive thiol (-SH) group of its cysteine residue, which can directly neutralise reactive oxygen species (ROS), reactive nitrogen species (RNS), and free radicals through electron donation.

Beyond direct scavenging, glutathione functions as a cofactor for the glutathione peroxidase (GPx) family of enzymes, which reduce hydrogen peroxide and lipid hydroperoxides to water and alcohols respectively. It also powers the glutathione S-transferase (GST) family, which conjugates glutathione to electrophilic toxins, drugs, and xenobiotics — marking them for excretion. This Phase II detoxification pathway is essential for eliminating environmental pollutants, drug metabolites, and carcinogens.

Glutathione also plays a critical role in immune function. It is required for the proliferation and activation of T lymphocytes and natural killer (NK) cells, and it regulates the redox state of immune cell signalling pathways. Melanin regulation is another documented effect — glutathione inhibits tyrosinase activity and shifts melanin production from darker eumelanin toward lighter pheomelanin, which underlies its researched skin brightening properties.

Glutathione was first discovered in 1888 by French chemist J. de Rey-Pailhade, who identified a substance in yeast he called 'philothion' (from Greek, 'love of sulphur'). The molecule was formally characterised as the tripeptide gamma-glutamylcysteinylglycine by Sir Frederick Gowland Hopkins in 1921, earning him the Nobel Prize in Physiology in 1929.

Research into glutathione's biological roles expanded dramatically from the 1960s onward, with Alton Meister's work establishing the gamma-glutamyl cycle and the central role of GSH in cellular detoxification. Since then, over 180,000 published papers reference glutathione, making it one of the most studied molecules in biochemistry. Its roles in aging, cancer prevention, immune function, liver health, and skin biology continue to generate active research worldwide.