Types of Antioxidants

1. Categorization by Origin

A. Internal Antioxidants (Endogenous)

• Definition: Antioxidants produced naturally by the body.
• Examples:
  • Superoxide Dismutase (SOD): Neutralizes superoxide radicals.
  • Glutathione: A key cellular antioxidant.
  • Catalase: Breaks down hydrogen peroxide into water and oxygen.
  • Coenzyme Q10 (Ubiquinone): Protects cell membranes and supports energy production.

B. External Antioxidants (Exogenous)

• Definition: Antioxidants obtained through diet, supplements, or topical applications.
• Examples:
  • Vitamins: Vitamin C, Vitamin E, Vitamin A (beta-carotene).
  • Minerals: Selenium, Zinc.
  • Polyphenols: Found in green tea, grapes, and dark chocolate (e.g., resveratrol, flavonoids).
  • Carotenoids: Lycopene (tomatoes), lutein (leafy greens).
  • Herbal Sources: Turmeric (curcumin), ashwagandha, and ginseng.

2. Categorization by Mechanism of Action

A. Primary Antioxidants (Preventive Antioxidants)

• Function: Directly neutralize free radicals by donating electrons or hydrogen atoms.
• Examples:
  • Vitamin C
  • Vitamin E
  • Glutathione

B. Secondary Antioxidants (Chain-Breaking Antioxidants)

• Function: Intervene in free radical chain reactions, breaking the chain to prevent further damage.
• Examples:
  • Polyphenols (e.g., flavonoids, resveratrol)
  • Carotenoids (e.g., beta-carotene, lutein)

C. Tertiary Antioxidants (Repair Antioxidants)

• Function: Repair oxidative damage and regenerate other antioxidants to maintain their effectiveness.
• Examples:
  • Enzymes like glutathione reductase (regenerates reduced glutathione).
  • Vitamin C (regenerates oxidized Vitamin E).

3. Other Classifications

A. Water-Soluble Antioxidants

• Act in aqueous environments (e.g., blood, cell cytoplasm).
• Examples:
  • Vitamin C
  • Glutathione

B. Fat-Soluble Antioxidants

• Protect cell membranes and lipids from oxidative damage.
• Examples:
  • Vitamin E
  • Beta-carotene
  • Coenzyme Q10

Practical Applications

1. Dietary Sources:
   • Vitamin C: Citrus fruits, strawberries, bell peppers.
   • Vitamin E: Nuts, seeds, and vegetable oils.
   • Polyphenols: Green tea, red wine, and dark chocolate.
   • Selenium: Brazil nuts, seafood, and whole grains.
2. Topical Antioxidants:
   • Vitamin C and Vitamin E in skincare products to combat oxidative stress on the skin.
   • Green tea extract for anti-aging properties.
3. Supplements:
   • Use supplements like glutathione, CoQ10, or resveratrol for targeted antioxidant support.