Antioxidants vs Oxidants

Prevent reactions with oxygen

causes and effects of oxidative stress

Causes and effects of oxidative stress
Causes and effects of oxidative stress

The origin of the term antioxidant is not medical or medicinal. This word was originally used to identify chemicals that prevent reactions with oxygen. It was in the late nineteenth and early twentieth centuries that the properties of antioxidants were widely studied for use in industrial processes to reduce such as metal corrosion and rubber vulcanization. In biology, the first research on antioxidants concerns the reduction of the oxidation of unsaturated fatty acids, due to rancidity. Antioxidant activity was easily measured by enclosing fats in containers sealed with oxygen and checking the rate of absorption of the latter. However, it was only with the identification of vitamins A, C and E that the importance of antioxidants in the biochemistry of living organisms was emphasized.

Oxidative stress appears to be one of the central mechanisms of cancer, cardiovascular disease and many other chronic diseases. Oxygen is essential for our survival, but its use by the body’s cells is not without danger. A significant portion (1-2%) of the oxygen we breathe is converted into toxic derivatives called free radicals (1). Free radicals can react and damage cellular components like proteins, lipids and DNA (2). The oxidation of biomolecules by free radicals is involved in several pathologies such as cardiovascular diseases (arteriosclerosis), neurodegenerative diseases (Parkinson’s, Alzheimer’s), cancer and aging (3–7).

Phytonutrient antioxidants and cell oxidation

Antioxidants are biological substances found in food that have the role of preventing oxidation reactions caused by free radicals. By definition, it is a substance with a low concentration compared to that of the oxidisable substrate, capable of delaying or stopping the oxidation of the substrate. In pictorial terms, the steel hull of a boat and the saline water that will make it rust for sure. The antioxidant? The paint that covers the hull and prevents it from attacking the metal. The more protective and thick the paint, the better the protection of the steel shell from rust.

Apple half oxidized the other not by the addition of lemon juice
Apple half of which is oxidized and the other not because we put lemon juice in it

If you saw a browned peeled apple, you saw the oxidation in action. Cover it with lemon and you will delay oxidation. Several enzymes and small molecules eliminate free radicals including phytonutrients and vitamins E and C (8). During aging, the generation of free radicals increases and their amount becomes greater than the capacity of antioxidant defenses. This imbalance, called oxidative stress, will lead the body to a pathological state (9).

Consumption rich in antioxidant compounds can mitigate the impact of this oxidative stress. In the scientific field antioxidants have been classified into three groups, namely:

– vitamins
– minerals
– phytonutrients (phytochemicals / phytoantoxydants).

During a balanced meal, these three groups of antioxidants are easily found, but the majority of dietary supplements contain synthetic antioxidants. It seems that antioxidants from food sources have a much higher bio activity than those from supplements from synthetic extracts. This is due on the one hand to the fact that foods contain greater heterogeneity of antioxidants and on the other hand, synthetic antioxidants are less well absorbed by the human body.

Classification of major classes of foodborne antioxidants

Table illustrating the different polyphenols
The classification of polyphenols

– Polyphenols

Polyphenols are chemical compounds naturally present in the plant kingdom, especially in northern berries. There are more than 8000 different phenolic molecules, such as simple molecules, such as phenolic acids, much more complicated molecules (tannins) and others that can be complexed to sugars, proteins and even lipids. Among the polyphenols, we find flavonoids which represent the main group of this series. Indeed, flavonoids are present throughout the plant kingdom, with the exception of fungi and algae. They are derivatives of hydrosolub polyphenols (soluble in water), often colorless or yellow (with exceptions, such as anthocyanins). Flavonoids are in themselves an extremely large family of compounds, playing important physiological roles (nutritional, medicinal, UV filters…). They are present in the berries of Quebec, and are of particular interest for human health. They are the subject of many medicinal claims, especially for their strong antioxidant capacity.

– Flavonoids

The flavonoids that have already been called vitamin P are not vitamins but have the same properties. Flavonoids are phytonutrients (phytochemicals). They represent a subclass of polyphenols that are found to be beneficial to human cells. Due to the variety of their pharmacological activities on mammals, flavanoids can also be referred to as nutraceutical (Topas et al., 2008).

Flavonoids are themselves classified according to their degree of oxidation into subgroups such as:

– flavonols
– flavones
– flavanols
– isolflavones
– proanthocyanins
– anthocyanins

– Isoflavones

Isoflavones are compounds found mainly in legumes (for example in soybeans whose phytoestrogenic properties are widely studied). Some isoflavone derivatives are powerful agents against certain bacteria. They have bacteriostatic properties and are specifically induced during infections by plant pathogenic organisms. In particular, many phytoalexins are found in legumes (e.g.: phaseollin from beans, glyceolline from soybeans)

– Proanthocyans (particularly concentrated in the case of cranberry /macrocarpon).

Proanthocyanidins (PACs), also called proanthocyanes or condensed tannins, are flavonoid compounds. Proanthocyanins are present in many plants, in

particular in the cranberry macrocarpon but also in the wild blueberry, in the skin and seeds of grapes and in several small wild fruits of Quebec such as lingonberry idaea.

Pro-anthocyanins are antioxidants with a strong protective power on human health. Both proanthocyans and anthocyanins help prevent certain cardiovascular diseases by curbing the effects of cholesterol in the heart and blood vessels.

– Anthocyanins (particularly concentrated in wild blueberries/ antigustifolium)

Blueberries and their anthocyanins
Blueberry anthocyanins

Anthocyanins are flavonoids found in the plant kingdom that give the characteristic color of leaves, flowers and fruits. These are colored compounds (orange, purple to blue) and usually water-soluble. Unlike other flavonoids, anthocyanins absorb most of the time in the ultraviolet spectrum. They play a major part in the coloration of petals, but they are also found in many plant tissues. Their synthesis in the leaf organs is often activated by stress (cold, deficiencies, senescence …). Their compounds are very often used as food dyes and exhibit antioxidant properties. Anthocyanins have been studied based on several biological activities including antioxidant capacity, effect on capillary vessel permeability and fragility, aggregation of blood platelets and effect on collagen (Ref 5 W). The antioxidant capacity of anthocyanins is one of the most important biological properties. Epidemiological and biomedical research suggests that antioxidants contained in berries, such as wild blueberries and cranberries macrocarpon may play a preventive role on the onset of certain diseases such as cancer, cardiovascular disease and neurodegenerative diseases such as Alzheimer’s and Parkinson’s. Anthocyanins and other flavonoids make a substantial contribution to the total antioxidants in the diet.

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