In many industries such as plastics, rubber, food, cosmetics, medicine, lubricants, etc., antioxidants are key additives used to prevent the performance of materials from deteriorating due to oxidation during storage, processing or use. Antioxidants not only determine the stability and life of the product, but also affect the safety and compliance of the final quality. For suppliers, a deep understanding of the mechanism of action of antioxidants is a key link in achieving technical empowerment and precise recommendations.
This article will analyze the scientific logic behind antioxidants for you around the three core mechanisms of action: free radical chain reaction blocking, metal chelation and oxidase inhibition.
1. Blocking free radical chain reaction: the core mechanism of antioxidants
Most oxidation processes are essentially free radical-mediated chain reactions. When a substance is subjected to external stimuli such as heat, light, mechanical shearing or metal catalysis, highly reactive free radicals are generated, which in turn trigger a chain reaction, leading to material degradation, oil rancidity or failure of active ingredients.
Antioxidants interrupt this chain reaction in the following ways:
● Three stages of chain reaction:
Initial stage: free radical formation (such as R•)
Extension stage: free radicals combine with oxygen to form peroxides (ROO•), which continue to attack stable molecules
Termination stage: two free radicals combine to form stable products, and the reaction terminates
● Intervention of antioxidants:
Hydrogen supply: antioxidants such as BHT and vitamin E can provide hydrogen atoms to free radicals, neutralizing them into stable molecules;
Chain termination: capture free radicals or intermediates to prevent them from continuing to diffuse;
Peroxide damage: decompose intermediates such as ROOH and ROO•, reducing the chain continuation ability.
✅ Typical applications:
Thermal oxidation aging protection in plastics and rubber
Preservation and rancidity delay of food and oils
Stable protection of anti-aging ingredients in cosmetics
II. Metal ion chelation: cutting off the oxidation "catalytic source"
In many systems, oxidation reactions are not only diffused by free radicals, but also strongly catalyzed by metal ions (such as Fe²⁺, Cu²⁺). These metals can accelerate the oxidation process of lipids and polymer materials under conditions such as light and heat.
Metal chelators in antioxidants can form stable coordination structures with these metals to prevent them from participating in oxidation reactions:
● Key points of chelation mechanism:
Multidentate molecules surround metal ions, making them lose their catalytic activity;
Typical structures such as carboxylic acids, phenolic hydroxyls, phosphates, etc. bind to metal ions;
Some natural ingredients (such as citric acid and phytic acid) have chelating effects.
✅ Typical applications:
Prevent color change and flavor deterioration in liquid dairy products, condiments, and beverages
Prevent odor caused by oil oxidation in skin care products
Prevent catalytic oxidation of metal debris in industrial lubricants
III. Inhibit oxidase activity: Block enzymatic oxidation pathways
In natural raw materials such as food, agricultural products, and plant extracts, enzymatic oxidation reactions can also cause browning, corruption, or degradation of functional components. Among them, polyphenol oxidase (PPO), **catalase (CAT)**, etc. are the main "villains".
Antioxidants can inhibit the activity of these enzymes in the following ways:
Structural denaturation: destroying the three-dimensional structure of the enzyme, making it inactive;
Competing with substrates for binding: preventing substrates (such as polyphenols) from entering the active site of the enzyme;
Chelating metal ions (such as copper) required by the enzyme, indirectly inhibiting enzyme activity.
✅ Typical applications:
Preventing browning in fruit and vegetable juices and sliced apples
Protecting active ingredients in agricultural product processing
Stabilizing polyphenols in plant extracts
