Flavanoid from green tea leaves brings much interest for people’s health

07/07/2011
Research by scientists from the Institute of Chemistry under Vietnam Academy of Science and Technology shows that flavanoid from green tea leaves can be used as medicine to treat cardiovascular diseases, high blood pressure, inflammation prevention, oxygenation prevention, as well as decrease the frequency of suffering from prostate cancer.
 

Vietnam is the world’s fourth-largest producer and exporter of tea. Therefore, we have to continue investment in researcher and development to ensure a quality product and make new values added products. Recent world research shows that several chemical elements of tea, especially EGCG, possess remarkable biological properties. Based on this, many new products for health protection and care have been developed from tea. This writing mentions flavonoid elements of tea, especially the possibility of subdividing and using kaempferol and myricetin compounds to treat diseases in humans.

Research projects show that drinking tea, especially green tea, has many possibilities of bringing usefulness to health, helping prevent several potentially fatal diseases such as blood pressure, obesity, diabetes and several types of cancer.

Extracts from tea contain phenolic compounds with flavon frame, divided into four major groups, including catechin (flavanol), oxygenation substances (theaflavin and thearubigin), proanthocyanidin and bisflavanol condensed substances, and flavonols. On the average, they account for 30% of ingredients in dried tea leaves.

 

 

Catechins (flavanol)

Catechins (flavanol) is the group which has highest content in green tea. Chemical form of tea catechins is presented in Figure 1. Most catechins consist of (-)-epigallocatechin 3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), (-)-epicatechin 3-gallate (ECG), và (+)-catechin (C). The most importance is EGCG, accounting for 50% of the general amount of phenol tea. EGCG is also considered to be most useful for health. In addition, other substances such as epiafzelechin and gallate as well as chemical catechin acetyls were also found.

 

 

 


Figure 1. Chemical form of tea catechins

 

Oxygenation substances

Theaflavin and thearubigin are used to mention substances causing the red brown for tea. They are created from catechins by oxygenation when fermenting. Figure 2 presents major theaflavins and their structures. Theaflavins in black tea are greater than in green tea. However, black tea has less catechins. The structure of thearubigins has not been verified.

 


Figure 2. Major theaflavins and their structures

 

Proanthocyanidin and bisflavanol condensed substances

 


Figure 3. Major proanthocyanidin and bisflavanol in tea

 

Tea has at least 16 different proanthocyanidin substances and is a natural raw materials rich in these substances. Figure 3 presents major proanthocyani and bisflavanol substances and their structures. Green tea contains much proanthocyanidin, and black tea contains much bisflavanol.

 

Flavonol

Major flavonols in tea are kaempferol, myricetin and quercetin substances in the form of mono-, di- and tri-O-glycoside (Figure 4). At least 14 substances were found. Flavonols rarely change in fermenting process. They are compositions which are good for health in tea without toxicity. After entering the body, they appear in the blood, showing activeness without hoard.

 


Figure 4. Major Flavonols in tea

 

Quercetin is used as nutritional supplement. Rutin is its glycoside and is used to make medicine to treat cardiovascular disease. Research projects also show that quercetin can prevent inflammation and oxygenation, and has many other effects.
Myricetin is an oxygenation substance. Research papers in vitro show that myricetin at high concentration can change LDL cholesterol thanks to its absorbtion intensification by white cells. A research project in Finland also mentions the relationship between high dose myricetin absorbtion and the reduce in the frequence of suffering from prostate cancer.

ACE enzyme inhibitor substances are useful in treating high blood pressure. A recent comparative research shows that kaempferol, not resveratrol, (two substances that western people take in much from fruit and wine) has this effect. Kaempferol also has antibiotic properties, which are not strong but can accord with other antibiotics such as clindamycin or erythromycin. Combining with strong activity to be against the process synthesizing melanin as well as COX inhibitor actives, kaempferol can have high effect in treating comedo diseases caused by greasy P.acnes virus.

An eight-year research paper affirmed that the appearance of three flavonol substances (including kaempferol, quercetin and myricetin) in daily food ingredients relates to the decrease in suffering from pancreatic cancer in smokers. This can be a conclusion to explain “Asian paradox” – the phenomenon in Asia where the rate of smokers is high with low rate of cancer.

Apart from the flavonoid group, tea also contains other valuable substances such as oil, carotenoids, vitamins, trace minerals and caffeine. Tea contains from 1.5 to 5% of caffeine, depending on each kind. Caffeine is also used with paraacetamol to make antifebrile medicine.

In summary, tea is a precious natural raw material which bring us many products with biological activity such as green tea extracts, tea phenol, EGCG, caffeine, tea seed powder and tea seed saponins. The paper proposed another subject needed to be further researched which is tea flavonols with the remarkable kaempferol and myricetin, extracted to make antibiotics.

 

Translated by Tuyet Nhung
Link to Vietnamese version



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