Classification of Natural Antioxidant Ingredients

This article classifies natural antioxidant ingedients, including flavonoids, polyphenols, natural pigments, vitamins and their derivatives, antioxidant peptides, and active polysaccharides. It elaborates on the composition, antioxidant mechanisms, and representative substances of each category. Natural antioxidants are safer and more effective, widely used in various fields.

 

 

Antioxidants act as hydrogen donors, scavenging free radicals generated during the chain initiation stage, effectively inhibiting the oxidation of oils. This makes them a commonly used method to delay oil oxidation and extend the shelf life of oils. Compared with synthetic antioxidants, which pose potential safety hazards such as teratogenicity, carcinogenicity, and the risk of chronic diseases, natural antioxidants are highly favored for their high safety, strong antioxidant capacity, absence of side effects, and preservative properties. According to their mechanisms of action, natural antioxidants can be classified into seven categories, including free radical scavengers, metal ion chelators, etc. The common types are mainly as follows:

 

1. Flavonoids

Flavonoids are natural plant components with a 2-phenylchromone structure that cannot be synthesized by the human body. Their antioxidant mechanisms are mainly twofold: first, they chelate metal ions, reducing the catalytic activity of metal ions and scavenging reactive oxygen species (ROS) and reactive nitrogen species; second, they scavenge free radicals by providing hydrogen atoms to form stable hydroperoxides, and the phenolic hydroxyl groups in the molecules react with oxygen free radicals to interrupt the free radical chain reaction. Common flavonoid antioxidants include:

• Peanut hull extract: It contains 3,4,5,7-tetrahydroxyflavone. Its antioxidant activity is comparable to that of butylated hydroxytoluene (BHT) and higher than that of tocopherol.
• TC-250 Oil for GYM Muscle Building: It contains liquiritigenin A, liquiritigenin B, and isoliquiritigenin, which can scavenge free radicals and inhibit enzymatic oxidation.
• Proanthocyanidins: They significantly inhibit oil oxidation, synergize with lecithin and vitamin E, and have the same effect as green tea polyphenols in inhibiting the activity of lipoxygenase.

In addition, flavonoids such as galangin, rutin in sophora flower buds, apigenin in oregano, and quercetin in Drosera burmanni also have antioxidant capacities equivalent to or higher than BHT.

2. Polyphenols

Polyphenols are a general term for chemical substances in plants with phenolic groups. They can be divided into two categories: polyphenol monomers, including chlorogenic acid, ellagic acid, and some complex polyphenol compounds with glycosides; and oligomers or polymers formed by the polymerization of polyphenol monomers, collectively known as tannins. For example:

• Green Tea extract polyphenols: Their antioxidant activity is 2.6 times that of butylated hydroxyanisole (BHA) and 3.6 times that of vitamin E. Since tea polyphenols are water-soluble, they need to be modified into an oil-soluble form to better function in oils.
• Resveratrol: It is mainly derived from plants such as peanuts, grapes (red wine), polygonum cuspidatum, and mulberries. Resveratrol, a polyphenol compound, is well-known for its effective activation of sirtuins. Sirtuins are important factors in delaying cellular senescence and extending lifespan by regulating various cellular processes. The inhibition of cellular senescence by sirtuins is mainly mediated by delaying age-related telomere attrition, maintaining genomic integrity, and promoting DNA damage repair.
•  

3. Natural Pigments

Natural pigments contain a large number of phenolic hydroxyl groups, enabling them to efficiently scavenge hydroxyl radicals and peroxyl radicals. They also have strong reducing properties and can quench singlet oxygen, making them highly promising natural oil antioxidants. Their antioxidant capacity is several times that of vitamins (such as vitamin C and vitamin E). Common natural pigments include β-carotene, lycopene, and astaxanthin. However, they have drawbacks such as poor water solubility, difficulty in color adjustment, and susceptibility to color change. Research shows that in rapeseed oil, the antioxidant effect is astaxanthin > lycopene > vitamin C > vitamin E > β-carotene > lutein; in soybean oil, it is astaxanthin > lutein > vitamin C ≈ vitamin E ≈ β-carotene > lycopene.

4. Vitamins and Their Derivatives

Vitamin C, vitamin E, and coenzyme Q10 are nutrients with strong antioxidant functions:

• Vitamin E: Also known as tocopherol, it can scavenge free radicals, eliminate potential sources of lipid peroxides, and maintain the integrity of cell membranes.
• Vitamin C: Also known as ascorbic acid, it is highly soluble in water and slightly soluble in acetone. Its antioxidant activity is mainly achieved by scavenging free radicals, converting into semidehydroascorbic acid through successive electron donation to remove radicals such as OH· and ROO·.
• Coenzyme Q10: A quinone compound widely present in cells of animals, plants, and microorganisms, usually in extremely low amounts. It exists in two forms in the body, oxidized and reduced, which can be converted into each other. Only the reduced form exhibits antioxidant activity, mainly manifested in scavenging free radicals, stabilizing cell membranes, and preventing apoptosis.

5. Antioxidant Peptides

Antioxidant peptides are derived from animal and plant proteins and their hydrolysates:

• Soybean peptides: Polypeptides formed by the enzymatic hydrolysis of soybean protein, which can strongly inhibit free radicals and the activity of lipoxygenase. The inhibition pathways include: â‘  chelating the Fe3+ at the active site of the enzyme; â‘¡ competing with the substrate for the active site of the enzyme; â‘¢ interacting with the enzyme molecule to affect or change the spatial structure of the enzyme, thereby reducing its activity.
• Glutathione: Composed of glutamic acid, cysteine, and glycine, abbreviated as GSH. The molecule contains a reduced sulfhydryl group (-SH), endowing it with antioxidant properties. Its antioxidant pathways include: â‘  blocking free radicals; â‘¡ binding to Hâ‚‚Oâ‚‚; â‘¢ scavenging lipid peroxides.

6. Active Polysaccharides

Active polysaccharides are high-molecular polymers formed by monosaccharides linked through glycosidic bonds. Panax ginseng polysaccharides and Bambusa multiplex polysaccharides have a good scavenging effect on ·OH; blueberry polysaccharides have strong scavenging effects on ·OH and DPPH radicals; ginger polysaccharides have a better scavenging effect on DPPH· than on ·OH.