Antioxidant Activity – Definition and Health Effects
Antioxidant activity describes the ability of substances to neutralize free radicals and reduce oxidative stress in the body, helping to protect cells from damage.
Things worth knowing about "Antioxidant Activity"
Antioxidant activity describes the ability of substances to neutralize free radicals and reduce oxidative stress in the body, helping to protect cells from damage.
What Is Antioxidant Activity?
Antioxidant activity refers to the capacity of a substance to neutralize free radicals and reactive oxygen species (ROS), or to prevent their formation in the first place. Free radicals are highly reactive molecules produced naturally during metabolic processes, but also generated by external factors such as UV radiation, cigarette smoke, air pollution, and poor dietary habits. When free radicals accumulate in excess, they cause oxidative stress, which can damage cells, proteins, lipids, and DNA.
Biological Importance
The human body possesses an intrinsic antioxidant defense system consisting of enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase. These enzymes work in concert with dietary antioxidants to keep oxidative stress in check. An imbalance between free radical production and antioxidant defenses is associated with a range of chronic diseases, including:
- Cardiovascular diseases
- Type 2 diabetes mellitus
- Neurodegenerative disorders (e.g., Alzheimer disease, Parkinson disease)
- Cancer
- Chronic inflammatory conditions
Sources of Antioxidant Activity
Endogenous Antioxidants
The body produces several antioxidant compounds internally. These include glutathione, uric acid, bilirubin, and the antioxidant enzymes mentioned above. Although these endogenous systems are essential for protection, they can become overwhelmed under conditions of high oxidative load.
Dietary Antioxidants
Many nutrients and phytochemicals obtained from food contribute significantly to antioxidant activity:
- Vitamin C (ascorbic acid): A water-soluble antioxidant that neutralizes free radicals in aqueous environments.
- Vitamin E (tocopherol): A fat-soluble antioxidant that protects cell membranes from lipid peroxidation.
- Beta-carotene and other carotenoids: Plant pigments with potent antioxidant properties.
- Polyphenols: Phytochemicals found in fruits, vegetables, tea, coffee, and red wine (e.g., flavonoids, resveratrol, quercetin).
- Selenium and zinc: Trace elements that act as cofactors for key antioxidant enzymes.
- Coenzyme Q10: A fat-soluble compound with antioxidant functions in the mitochondria.
Measuring Antioxidant Activity
Several laboratory methods are used to quantify the antioxidant activity of foods, plant extracts, or biological samples. The most widely used include:
- DPPH assay: Measures the ability of a substance to reduce the stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl).
- FRAP assay (Ferric Reducing Antioxidant Power): Assesses the capacity to reduce ferric ions.
- ORAC assay (Oxygen Radical Absorbance Capacity): Measures the absorption capacity against oxygen radicals.
- TEAC assay (Trolox Equivalent Antioxidant Capacity): Compares antioxidant activity relative to the reference compound Trolox.
These methods are widely applied in food science and pharmacology to quantify and compare the antioxidant potential of different substances.
Antioxidant Activity and Health
A balanced diet rich in fruits, vegetables, whole grains, legumes, and nuts is considered the most effective strategy for maintaining high antioxidant capacity in the body. The World Health Organization (WHO) recommends consuming at least 400 g of fruits and vegetables daily to ensure an adequate supply of antioxidant nutrients.
Supplementation with isolated antioxidants (e.g., high-dose vitamin E or beta-carotene) has not consistently demonstrated the expected health benefits in clinical trials and may even produce adverse effects at very high doses. Experts therefore recommend obtaining antioxidants primarily through a natural, plant-rich diet rather than through supplements.
Antioxidant Activity in the Food Industry
In food processing, antioxidants are also used as food additives to prevent the oxidative spoilage of fats and oils and to extend product shelf life. Well-known examples include vitamin C (E300), vitamin E (E306-E309), and synthetic antioxidants such as BHA (E320) and BHT (E321).
References
- World Health Organization (WHO): Diet, nutrition and the prevention of chronic diseases. WHO Technical Report Series 916, Geneva, 2003.
- Halliwell B, Gutteridge JMC: Free Radicals in Biology and Medicine. 5th edition, Oxford University Press, 2015.
- Lobo V, Patil A, Phatak A, Chandra N: Free radicals, antioxidants and functional foods: Impact on human health. Pharmacognosy Reviews, 2010; 4(8): 118-126. PubMed PMID: 22228951.
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