Tea Polyphenols: Composition, Benefits and Metabolism

Tea polyphenols (TPs) have certain antioxidant, anti-tumor, lipid-lowering, liver-protecting and kidney-protecting activities. It is widely used in food field and medical research. Therefore, by elaborating the function and mechanism of tea polyphenols, it provides a reference for the application of the biological activity mechanism of tea polyphenols.

Tea Polyphenols Composition

The main components of TPs include catechin metabolites, theaflavins, and phenolic acids. Catechin metabolites account for about 70% of the total TPs. Epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) are the main components of catechins. EGCG has the highest content, accounting for about 65% of the total catechins.

Tea Polyphenols Function

TPs are a class of bioactive compounds with various functional properties, such as antioxidant, antibacterial, antiviral, anti-inflammatory, diabetes prevention, hypolipidemic and hypoglycemic effects.

1. Antioxidant: At present, tea polyphenols have become one of the most important natural antioxidants. The reactive hydroxyl groups present in TPs molecules can interact with and scavenge free radicals (such as peroxy radicals, hydroxyl radicals) generated during the oxidation of triglycerides in food systems (such as fats, oils, and emulsions). Thus, the radical chain reaction is terminated.

2. Antibacterial: Studies have shown that tea polyphenols have a good inhibitory effect on a variety of pathogenic bacteria and plant-derived fungi. In addition, when tea polyphenols are used in combination with organic acids (such as malic acid, tartaric acid, benzoic acid, etc.), bacteriocins such as nisin, or chelating agents such as EDTA, their antibacterial activity is enhanced.

3. Prevention of diabetes: Tea polyphenols can enhance insulin action by reducing insulin resistance, scavenging free radicals and reducing inflammation, thereby preventing and treating diabetes and complications. A study showed that in China, people who drink tea regularly have a 50% lower risk of developing diabetes than those who do not drink tea. Drinking more than 1 cup of tea a day reduces the risk of diabetes by 14%.

4. Other functional activities: Tea polyphenols also have various activities such as antiviral, liver protection, cholesterol lowering, neuroprotection and anti-obesity.

Metabolism and Biotransformation

Existing studies have shown that when tea polyphenols enter the human body, they are mainly metabolized in the liver. Small amounts are metabolized or biotransformed by gut microbes.

After being metabolized by the liver, the metabolites further enter other tissues and kidneys, and are finally excreted in bile and urine. In addition, polyphenols that are not metabolized will circulate in the blood in a free state.