How do antioxidants work
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Understanding How Antioxidants Work
Introduction to Antioxidants and Their Importance
Antioxidants are substances that can delay or prevent the oxidation of other molecules, thereby protecting cells from damage caused by free radicals and reactive oxygen species (ROS) 14. These compounds are crucial in maintaining health and preventing chronic diseases such as cancer, diabetes, and heart disease 67.
Mechanisms of Antioxidant Action
Hydrogen Atom Transfer (HAT) and Single Electron Transfer (SET)
Antioxidants neutralize free radicals through several mechanisms, primarily hydrogen atom transfer (HAT) and single electron transfer (SET). In HAT, antioxidants donate a hydrogen atom to free radicals, neutralizing them. In SET, antioxidants donate an electron to free radicals, stabilizing them . These mechanisms are essential for understanding the biological roles of antioxidants and their potential applications .
Chelation of Transition Metals
Another critical mechanism is the chelation of transition metals, which can catalyze the formation of free radicals. By binding to these metals, antioxidants prevent them from participating in reactions that generate free radicals .
Enzymatic Removal of Nonradical Electrophiles
In vivo, the scavenging of free radicals by antioxidants is often ineffective due to kinetic constraints. Instead, antioxidants primarily function by enzymatically removing nonradical electrophiles, such as hydroperoxides, through two-electron redox reactions . This process is crucial for maintaining cellular health and preventing oxidative damage.
Types of Antioxidants
Low Molecular Weight Scavengers
Intracellular antioxidants include low molecular weight scavengers like ascorbate (vitamin C) and glutathione, which neutralize oxidizing species through one-electron or hydrogen atom transfer . Ergothioneine is another scavenger that specifically targets hypervalent ferryl complexes and other reactive species .
Hydrophobic Scavengers
Hydrophobic antioxidants, such as alpha-tocopherol (vitamin E) and carotenoids, are found in cell membranes where they inhibit lipid peroxidation chain reactions . These antioxidants play a vital role in protecting cellular structures from oxidative damage.
Antioxidant Enzymes
Key antioxidant enzymes include superoxide dismutases (SOD), catalases, and peroxidases like glutathione peroxidase (GPx) and ascorbate peroxidase (APx). These enzymes degrade superoxide and hydroperoxides, preventing the formation of harmful free radicals 36.
Antioxidants in Diet and Health
Dietary antioxidants, such as vitamins E and C, carotenoids, and flavonoids, are essential for supplementing the body's endogenous antioxidant defenses 47. These compounds are found in various fruits, vegetables, and other plant-based foods and are crucial for maintaining health and preventing oxidative stress-related diseases 47.
Conclusion
Antioxidants play a vital role in protecting cells from oxidative damage through various mechanisms, including hydrogen atom transfer, single electron transfer, and chelation of transition metals. They are found both endogenously and in the diet, with dietary antioxidants being crucial for supplementing the body's defenses. Understanding these mechanisms and the types of antioxidants can help in developing strategies to prevent and treat oxidative stress-related diseases.
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