Antioxidant

An antioxidant is a substance that slows or prevents oxidation by reacting with oxidizing agents or interrupting oxidation reactions. Antioxidants act in chemical systems, foods, and living organisms.

Free radical: An atom, molecule, or ion with an unpaired electron, often making it chemically reactive. Many antioxidants interrupt oxidation by reacting with free radicals before they attack other molecules.
Oxidation: A chemical process in which a substance loses electrons or increases its oxidation state. Antioxidant action is defined by its ability to slow oxidation reactions.
Food preservation: Methods used to slow spoilage and maintain the safety or quality of food. Antioxidants delay rancidity and discoloration caused by oxidation in foods.
Pro-oxidant: A substance or condition that promotes oxidation or increases reactive species in a particular system. Some antioxidants can promote oxidation under certain conditions, especially depending on dose and metal availability.
Chain reaction: A sequence in which one reaction produces a species that triggers further reactions. Lipid oxidation propagates through radical chain reactions that some antioxidants terminate.
Reactive oxygen species: Oxygen-containing molecules and ions that readily participate in chemical reactions. Several reactive oxygen species initiate or propagate the reactions antioxidants can suppress.
Vitamin E: A group of fat-soluble compounds, including tocopherols, that function as nutrients and antioxidants. Its lipid solubility helps protect membranes and oils from oxidation.
Antioxidant paradox: The mismatch between plausible antioxidant mechanisms and the limited or inconsistent benefits of many antioxidant supplements. It captures why laboratory antioxidant activity does not guarantee improved health.
Redox reaction: A chemical reaction in which electrons transfer between substances, changing their oxidation states. Antioxidant activity is one outcome of electron-transfer chemistry.
Oxidative stress: A condition in which oxidant production exceeds the capacity of biological defenses and repair. Antioxidants are often discussed as defenses against this imbalance, though they do not define it.

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