OxPhos? is a medium based metabolic probe that can measure glutathione recycling capacity/glutathione function and glucose dependent antioxidant capacity of cells in tissue culture and whole blood. Oxphos? is based on the ability of mammalian cells to rapidly and efficiently convert hydroxyethyl disulfide (HEDS) into mercaptoethanol (ME) through a bioreduction mechanism. Bioconversion of HEDS to ME relies on the activity of the oxidative pentose phosphate cycle (OPPC). OxPhos? measures ME in the extracellular medium without the need for cellular lysis and extraction methods. Cell media is used in the assay, avoiding the need to lyse cells and thereby saving time and cost while preserving the ability to perform other cellular tests in the same culture system. OxPhos? may have multiple applications in aging, oxidative stress, antioxidant screening, chemotherapy response and toxicology. Synonyms: Glutathione recycling, glutathione function, and glucose dependent antioxidant capacity assay, cell viability, cell survival cellular viability, cellular survival, antioxidant assay