Antioxidant
A substance that neutralises reactive oxygen species and prevents oxidative damage to cells. Endogenous antioxidants include glutathione, superoxide dismutase, and catalase. Some research peptides are investigated for antioxidant properties that may provide cytoprotective benefits.
Technical Context
Endogenous antioxidant systems: enzymatic (SOD — converts O2•⁻ → H2O2, three isoforms: Cu/Zn-SOD cytoplasmic, Mn-SOD mitochondrial, EC-SOD extracellular; catalase — converts H2O2 → H2O + O2, primarily in peroxisomes; glutathione peroxidase — converts H2O2 and lipid hydroperoxides → H2O using glutathione as electron donor; thioredoxin reductase — maintains thioredoxin in reduced state for protein repair) and non-enzymatic (glutathione — the most abundant intracellular antioxidant, tripeptide Glu-Cys-Gly; vitamin C/ascorbic acid — aqueous-phase radical scavenger, also cofactor for collagen synthesis; vitamin E/α-tocopherol — lipid-phase antioxidant protecting membranes; uric acid; bilirubin). Some peptides have intrinsic antioxidant properties — His and Trp residues can scavenge ROS, and metal-binding peptides (like GHK-Cu) can modulate redox chemistry. However, exogenous antioxidant supplementation trials have generally failed to show clinical benefits for disease prevention.