Antioxidants are substances that prevent or reduce oxidative damage by neutralizing reactive oxygen species (ROS) and other free radicals. They can be classified into endogenous (produced within the body) and exogenous (obtained from the diet or supplements). Here is a comprehensive list of antioxidants categorized based on their sources and types:
1. Endogenous Antioxidants (Produced by the Body)
Enzymatic Antioxidants:
- Superoxide Dismutase (SOD):
- Converts superoxide radicals (O₂⁻) into hydrogen peroxide (H₂O₂).
- Exists in different forms:
- Cu/Zn-SOD: Found in the cytoplasm.
- Mn-SOD: Found in mitochondria.
- Fe-SOD: Found in prokaryotes.
- Catalase:
- Converts hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂).
- Glutathione Peroxidase (GPx):
- Reduces hydrogen peroxide and lipid peroxides using glutathione.
- Glutathione Reductase:
- Regenerates reduced glutathione (GSH) from its oxidized form (GSSG).
- Peroxiredoxins (Prx):
- Detoxify peroxides, including hydrogen peroxide and organic peroxides.
- Thioredoxin:
- Reduces oxidized proteins by donating electrons.
Non-Enzymatic Antioxidants:
- Glutathione (GSH):
- A tripeptide involved in detoxification and free radical scavenging.
- Uric Acid:
- Neutralizes free radicals in plasma.
- Coenzyme Q10 (Ubiquinone):
- Protects mitochondrial membranes and recycles vitamin E.
- Alpha-Lipoic Acid (ALA):
- A universal antioxidant that is both water- and fat-soluble.
- Melatonin:
- Scavenges free radicals and protects against oxidative damage.
2. Exogenous Antioxidants (Obtained from Diet)
Vitamins:
- Vitamin C (Ascorbic Acid):
- Water-soluble; neutralizes ROS in the aqueous phase.
- Vitamin E (Tocopherols and Tocotrienols):
- Fat-soluble; protects cell membranes from lipid peroxidation.
- Vitamin A (Retinol) and Beta-Carotene:
- Scavenge free radicals and protect lipid membranes.
Minerals (Cofactors for Antioxidant Enzymes):
- Selenium:
- Essential for glutathione peroxidase activity.
- Zinc:
- Stabilizes cell membranes and supports SOD activity.
- Copper:
- Cofactor for Cu/Zn-SOD.
- Manganese:
- Cofactor for Mn-SOD.
- Iron (in controlled amounts):
- Cofactor for catalase.
Plant-Derived (Phytochemicals):
- Flavonoids:
- Found in fruits, vegetables, tea, and wine (e.g., quercetin, catechins, anthocyanins).
- Polyphenols:
- Resveratrol (grapes, red wine), curcumin (turmeric), ellagic acid (berries).
- Carotenoids:
- Lycopene (tomatoes), lutein (green leafy vegetables), zeaxanthin (corn).
- Tannins:
- Found in tea, coffee, and berries.
- Sulfur-Containing Compounds:
- Allicin (garlic), sulforaphane (broccoli).
- Isothiocyanates:
- Found in cruciferous vegetables (e.g., kale, cabbage).
- Chlorophyll:
- Found in green plants, offers mild antioxidant properties.
Other Dietary Antioxidants:
- Omega-3 Fatty Acids (EPA and DHA):
- Reduce oxidative stress in cell membranes.
- Carnosine:
- Found in meat; protects proteins from oxidation.
- Taurine:
- Found in seafood and meat; neutralizes ROS.
- Proanthocyanidins:
- Found in grapes, chocolate, and berries.
- Catechins:
- Found in green tea.
3. Synthetic Antioxidants (Supplements/Pharmaceuticals)
- Butylated Hydroxytoluene (BHT) and Butylated Hydroxyanisole (BHA):
- Used as food preservatives; mimic natural antioxidants.
- N-Acetylcysteine (NAC):
- A precursor to glutathione, widely used to boost antioxidant defenses.
- Trolox:
- A water-soluble analog of Vitamin E.
- Edaravone:
- Used in the treatment of oxidative stress-related diseases (e.g., ALS).
Conclusion
Maintaining a balance between these antioxidants and oxidative stress is crucial for health. Incorporating a diverse range of antioxidant-rich foods and leading a healthy lifestyle helps bolster the body’s defenses.