FLAVONOIDS

 FLAVONOIDS

Flavonoids are low molecular weight phenolic compounds with significant antioxidant and chelating properties. They are isolated from a vast range of vascular plants with over 8000 individual compounds known. In the human diet, they are most concentrated in fruits, vegetables, wines, teas, and cocoa. Flavonoids exhibit biological activities including anti-allergenic, antiviral, anti-inflammatory, and vasodilating actions. However, the most interesting property is the antioxidant property as it is associated with various health benefits including chronic diseases such as cardiovascular disease, cancer, and neurodegenerative disorder due to the ability to reduce free radical formation. The effectiveness of Flavonoids depends on their structure, concentration, and interactions with other compounds in the body. The structure of flavonoids consists of 15 carbon skeletons and two aromatic rings connected by a three-carbon chain which is usually an oxygenated heterocyclic pyran. Six subclasses of flavonoids are defined: flavones; flavonols; flavanones; flavan-3-ols; isoflavones; chalcones and anthocyanosides.

FLAVONOIDS AS ANTIOXIDANTS

1. Scavenging of Free Radicals: -

Oxidation is essential in aerobic life and metabolism as oxygen accepts electrons in the electron flow, producing ATP. However, uncoupling of electron flow generates harmful free radicals, including superoxide, peroxyl, alkoxyl, hydroxyl, and nitric oxide. Other damaging ROS in living organisms are singlet oxygen, hydrogen peroxide, and hypochlorous acid. ROS have positive roles in energy production, cell regulation, signaling, and synthesis of important compounds. Yet, they can attack lipids, proteins, carbohydrates, and DNA, causing membrane damage, protein modification, and DNA damage. Excessive ROS production and oxidative stress are linked to cardiovascular diseases, neurodegenerative disorders, cancer, diabetes, and inflammation

2. Metal Chelation: -

Flavonoids have the ability to bind to transition metal elements such as Cu+, Fe2+ which can catalyze the formation of free radicals. By chelating these metal ions, flavonoids inhibit their pro-oxidant activity thus reducing the oxidative stress. The chelation process involves the donation of electrons from the flavonoid to the metal ion, creating a stable coordination bond.

H2O2 + Fe2+(Cu+) → • OH + OH- + Fe3+(Cu2+)

In summary, flavonoids exhibit metal chelation properties by binding to metal ions through their hydroxyl groups. Metal chelation is one of the mechanisms through which flavonoids exert their antioxidant effects and may contribute to their biological activities and potential health benefits.

3. Modulation of enzymatic antioxidant defence: -

Flavonoids interact and modulate the activity of various antioxidant enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase. They can enhance the expression or activity of these enzymes, leading to improved antioxidant defense within cells. These enzymes work together to neutralize free radicals and maintain cellular redox balance thereby protecting cells from oxidative damage.

4. Anti-Inflammatory effects: -

Flavonoids possess anti-inflammatory properties which are closely related to antioxidant activity. Inflammation can lead to the production of ROS, and flavonoids can suppress the process by inhibiting pro-inflammatory enzymes and cytokines. By reducing inflammation flavonoids indirectly contribute to the antioxidant defense.

5. Regeneration of other Antioxidant: -

Flavonoids can regenerate other antioxidants such as vitamins C and E, Glutathione, and coenzyme Q10. These antioxidants play important roles in neutralizing free radicals, but they can become oxidized in the process. Flavonoids can restore their antioxidant properties, enhancing their effectiveness in combating oxidative stress.