mechanismsantioxidant

Mechanisms of antioxidants describe how antioxidant molecules and systems counteract oxidative stress. Antioxidants can be endogenous or dietary and function by multiple overlapping mechanisms to limit oxidative damage to lipids, proteins, and nucleic acids, and to modulate redox signaling.

Direct scavenging involves donating electrons or hydrogen atoms to neutralize reactive oxygen and nitrogen species such as superoxide, hydroxyl, and peroxyl radicals, effectively terminating radical chain reactions. Some antioxidants act as chain-breaking terminators that interrupt propagation steps in lipid peroxidation.

Metal ion chelation reduces the catalytic activity of transition metals like iron and copper that drive radical generation through Fenton chemistry, thereby reducing the production of highly reactive species.

Regeneration and maintenance of redox networks occur when antioxidants restore each other to active forms. For example, vitamin C can regenerate vitamin E, while glutathione and the thioredoxin system participate in redox cycling and protein repair.

Induction of endogenous defenses is another mechanism. Many antioxidants or related compounds activate transcription factors such as Nrf2, leading to increased expression of detoxifying and antioxidant enzymes including superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferases.

Context and scope: Endogenous antioxidants include enzymes and small molecules such as glutathione, uric acid, and thiols; dietary antioxidants include vitamins C and E, carotenoids, and polyphenols. Some antioxidants also modulate redox signaling, influencing gene expression and cellular responses beyond direct radical scavenging.

Clinical relevance: Oxidative stress is associated with aging and various diseases, but antioxidant supplementation has yielded mixed results in trials, highlighting the complexity of redox biology and the need for balanced antioxidant defenses rather than simple overconsumption.