Tea polyphenols, also known as antioxidants, vitamin polyphenols and tetrandrine, are a kind of polyhydroxy compounds contained in tea, referred to as TP. The main chemical components are catechins (flavanols), flavonoids and flavonols, anthocyanins, phenolic acids and peptides, polymeric phenols and other compounds. Among them, catechin is the main component of tea polyphenols, accounting for 65%~80% of the total tea polyphenols. Catechin compounds mainly include catechin (EC), epigallocatechin (EGC), catechin gallate (ECG) and epigallocatechin gallate (EGCG).
raw material
It is a condensed aromatic hydrocarbon, which can be divided into flavanols, hydroxy -[4]- flavanols, anthocyanins, flavonoids, flavonols and phenolic acids. Among them, catechin is the most important, accounting for about 60%-80% of total polyphenols; Catechins are mainly composed of several monomers such as EGC, DLC, EC, EGCG, GCG and ECG. The content of tea polyphenols in tea is generally 20-35%. The main component of tea polyphenols is flavanol, and flavanol is catechin. The content of catechin accounts for about 70% of the total amount of tea polyphenols.
Character; Role; letter
Tea polyphenols are light yellow to brown tea perfume solution, powdery solid or crystal, astringent in taste, easily soluble in water, ethanol and ethyl acetate, and slightly soluble in oil. Good heat and acid resistance, very stable in the range of pH2~7. Slightly hygroscopic, the pH value of the aqueous solution is 3 ~ 4. It is easy to oxidize and turn brown under alkaline conditions. When it meets iron ions, it will produce green-black compounds.
perform
Tea polyphenols have a strong antioxidant effect, especially ester catechin EGCG, and its reducibility can even reach 100 times that of L- isocitrate. Among the four main catechins, the antioxidant capacity is EGCG >；; EGC & gt； Electrocardiogram & gtEC & gtBHA, the antioxidant capacity increases with the increase of temperature. Tea polyphenols not only have antioxidant effect, but also have antibacterial effect, such as inhibiting staphylococcus, Escherichia coli, Bacillus subtilis and so on. Tea polyphenols can adsorb the odor in food, so it has a certain deodorizing effect. It can protect the pigment in food, it can not only play the role of natural pigment, but also prevent food from fading. Tea polyphenols can also inhibit the formation and accumulation of nitrite.
physicochemical property
physical features
Tea polyphenols are light yellow or light green powder at room temperature, and are easily soluble in warm water (40℃-80℃) and aqueous ethanol. The stability is extremely strong, and it can remain stable for 65438 0.5 hours in the environment of pH 4-8 and 250℃, and it is easy to decompose under ferric ions. 1989 was listed as GB2760-89 standard for food additives by China Food Additives Association, and 1997 was listed as raw material of Chinese patent medicine.
chemical property
Tea polyphenol is a natural antioxidant food extracted from tea, which has the characteristics of strong antioxidant capacity, no toxic side effects and no odor.
Tea polyphenols refer to a large class of polyphenols and their derivatives in tea, with complex composition and great differences in molecular weight and structure. They are mainly organic compounds composed of catechins, flavonols, anthocyanidins, phenolic acids and their peptides. Flavonoids and alcohols mainly containing catechins account for 60%-80% of the total amount of tea polyphenols, among which L-EGCG (50%-60%) and L-EGC (60%) have the highest contents.
pharmacological action
be anticancer
Tea polyphenols can scavenge harmful free radicals, block the process of lipid peroxidation, and improve the activity of enzymes in human body, thus playing an anti-mutation and anti-cancer role.
green tea
Efficacy. According to relevant data, tea polyphenols (mainly catechins) in tea are beneficial to the prevention and adjuvant treatment of cancers such as gastric cancer and intestinal cancer.
Tea polyphenols play an important role in preventing cardiovascular diseases, lowering blood lipid and preventing liver and coronary atherosclerosis. The content of cholesterol and triglyceride in human body is high, fat is deposited on the inner wall of blood vessels, and vascular smooth muscle cells proliferate to form atherosclerotic plaques and other cardiovascular diseases. Tea polyphenols, especially catechins ECG and EGC in tea polyphenols and its oxidation products theaflavins, are helpful to inhibit this mottled proliferation, reduce the formation of fibrinogen that enhances coagulation viscosity, make coagulation clear, and thus inhibit atherosclerosis. Antihypertensive tea polyphenols have a strong inhibitory effect on invertase activity, so it can reduce or keep blood pressure stable. Hypoglycemic tea polyphenols can regulate the disorder of glucose metabolism and reduce the blood sugar level, thus effectively preventing and treating diabetes.
Prevention and treatment of stroke
Tea polyphenols can inhibit the production of lipid peroxide, eliminate vasospasm, maintain the elasticity of blood vessel wall, increase the effective diameter of blood vessel, and reduce blood pressure through vasodilation, thus effectively preventing stroke.
Anti-thrombotic
The increase of plasma fibrinogen can cause the aggregation of red blood cells and the increase of blood viscosity, thus promoting thrombosis. In addition, the increase of phospholipids and cholesterol in cell membrane lipids will reduce the deformability of red blood cells, seriously affect the perfusion of microcirculation, increase blood viscosity, make capillary blood flow stagnate, and aggravate red blood cell aggregation and thrombosis.
Tea polyphenols can protect and repair erythrocyte deformability, easily form a complex with thrombin, and prevent fibrinogen from becoming fibrin. In addition, tea polyphenols can effectively inhibit the increase of cholesterol content in plasma and liver, promote the excretion of lipids and bile acids, and thus effectively prevent the formation of thrombosis. Most of the existing lipid-lowering and antithrombotic drugs have certain toxic and side effects and are not easy to take for a long time. Tea polyphenol is a natural component with lipid-lowering and antithrombotic effects in tea, and its antioxidant properties make it a new functional health care product.
improve immunity
① By regulating the activity of immunoglobulin, it can indirectly improve comprehensive immunity, resist rheumatism factors, and resist bacteria and viruses.
Tea polyphenols can increase the total amount of human immunoglobulin and keep it at a high level, thus stimulating the change of antibody activity and improving people's overall immune ability. Indirectly realize the efficacy of inhibiting or killing various pathogens, germs and viruses.
Deoxyribonucleic acid
② allergic reaction and skin allergic reaction.
Tea polyphenols can strongly inhibit the release of histamine. Experiments show that the antiallergic effect of tea polyphenols is 2~ 10 times stronger than that of common antiallergic drugs. Tea polyphenols can inhibit allergic reactions caused by antibodies, adrenaline, enzymes and other active factors, and have a significant effect on allergic diseases such as asthma.
③ Relieve gastrointestinal tension, stop diarrhea and induce diuresis.
Tea polyphenols can stimulate gastrointestinal reaction, accelerate large intestine peristalsis, and achieve the effect of treating constipation.
Tea polyphenols can inhibit and kill all kinds of harmful pathogens causing diarrhea by improving the comprehensive immune ability of human body, and relieve gastrointestinal tension, thus achieving the effect of diminishing inflammation and stopping diarrhea.
Flavonoids and alcohols in tea polyphenols can stimulate renal vasodilation and increase renal blood flow, thus improving glomerular filtration rate and eliminating lactic acid in urine. Lactic acid in human muscles and tissues is a kind of fatigue substance, which can be excreted to restore the tired body.
④ Promote the absorption of Vc and prevent scurvy.
Tea polyphenols can promote the absorption of vitamin C, thus effectively preventing and treating septicemia.
Other health care effects
① Anti-lipid peroxidation and anti-aging.
Tea polyphenols can scavenge free radicals and inhibit lipoxygenase and lipid peroxidation in skin mitochondria, thus having anti-aging effect. Studies show that the antioxidant activity of tea polyphenols is obviously better than that of vitamin E, and it has synergistic effect with vitamins C and E. ..
② Anti-dissolution effect on heavy metal salt and alkaloid poisoning.
Tea polyphenols have a strong adsorption effect on heavy metals, and can form complexes with heavy metals to produce precipitates, which is conducive to reducing the toxic effects of heavy metals on human bodies. In addition, tea polyphenols can also improve liver function and diuresis, so it has a good anti-dissolution effect on alkaloid poisoning.
③ Prevent radiation injury and reduce the adverse reaction of radiotherapy.
Tea polyphenols and its oxidation products have excellent anti-radiation function, which can absorb radioactive substances and prevent them from spreading in human body. They are called natural ultraviolet filters. As an adjuvant therapy, tea polyphenols can effectively maintain the stability of white blood cells, platelets and hemoglobin levels; Improve the adverse reactions caused by radiotherapy and chemotherapy; Effectively relieve the inhibition of radiation on the weight gain of bone marrow cells; Effectively reduce the inhibitory effect of radiotherapy and chemotherapy drugs on the immune system of the body.
④ The function of preventing caries, strengthening teeth and eliminating halitosis.
Tea polyphenols can kill dental caries bacteria such as lactic acid bacteria in teeth, and inhibit the activity of glucose polymerase, so that bacteria can not colonize teeth, effectively blocking the process of dental caries formation. Protein food left in teeth becomes the substrate for the propagation of spoilage bacteria, and tea polyphenols can kill these bacteria.
⑤ Digestive aid
Tea polyphenols can enhance gastrointestinal peristalsis and prevent digestive organ diseases. In addition, tea polyphenols can be attached to the wound of the stomach in a thin film state, which plays a protective role in the ulcer wound.
6. Conducive to beauty and skin care.
Tea polyphenols are water-soluble substances, which can remove greasy face and astringe pores, and have the effects of disinfection, sterilization, anti-aging and reducing the damage of ultraviolet rays in the sun to the skin. Tea polyphenols can block ultraviolet rays and remove free radicals induced by ultraviolet rays, thus protecting the normal function of melanocytes and inhibiting the formation of melanin. At the same time, it inhibits lipid oxidation and reduces pigmentation.
Main applications
brief introduction
Tea polyphenols has a strong antioxidant effect, its antioxidant capacity is 4-6 times that of synthetic antioxidants BHT and BHA, 6-7 times that of ve and 5- 10 times that of VC, and it can take effect when the dosage is small: 0.0 1-0.03%, and there is no potential toxic and side effect of the composition; Catechin can protect the pigments and vitamins in food, keep the original color and nutritional level of food for a long time, effectively prevent the corruption of food and edible oil, and eliminate the odor.
In fact, many functions of tea are due to tea polyphenols in tea. Tea polyphenols can be used for food preservation and anti-corrosion, with no toxic and side effects, safe to eat, and better anti-corrosion effect with phytic acid. Tea can be preserved for a long time without deterioration, which is beyond the reach of other leaves, vegetables and flowers. Adding tea polyphenols to other organic substances (mainly food) can prolong the shelf life, prevent food from fading, improve the stability of cellulose and effectively protect various nutritional components of food. Its main uses are as follows:
Pastry and dairy products
For high-fat cakes and dairy products, such as moon cakes, biscuits, cakes, instant noodles, milk powder, cheese, milk and so on. Adding tea polyphenols can not only keep its original flavor, prevent corruption, prolong shelf life, prevent food from fading, inhibit and kill bacteria, improve food hygiene standards and prolong food sales life. In addition, it can make the sweet "sour tail" disappear and taste sweet.
Beverage production
Tea polyphenols can not only make fruit-flavored tea, lemon tea and other drinks, but also inhibit the degradation and destruction of vitamins such as VA and VC in soybean milk, soda and fruit juice, thus ensuring various nutritional components in the drinks.
Preservation of fruits and vegetables
Spraying low-concentration tea polyphenols solution on fresh fruits and vegetables can inhibit bacterial reproduction, maintain the original color of fruits and vegetables, and achieve the purpose of preservation and antisepsis.
Livestock meat products
Tea polyphenols have good quality preservation and anti-loss effects on meat and its pickled products, such as sausages and canned bacon, especially on heat-resistant spores in canned food, and have the functions of eliminating odor and fishy smell and preventing oxidation discoloration.
Edible oil storage
Adding tea polyphenols to edible oil can prevent and delay the automatic oxidative decomposition of unsaturated fatty acids, thus preventing the qualitative change and corruption of oil and prolonging the storage life of oil and fat by more than one time.
limitations on use
According to China's Hygienic Standard for the Use of Food Additives (GB 2760-20 1 1), the range and dosage of tea polyphenols are as follows:
(g/kg): basically anhydrous grease, 0.4; Cooked nuts and seeds, 0.2; Fried noodle products, 0.2; Instant grain, including oatmeal (slice) 0.2; Instant rice flour products 0.2.
In addition, caffeine, also known as caffeine, is a by-product of tea polyphenols. It is a white crystal or powder, which can excite the cerebral cortex when dissolved in water and ethanol, so it has a refreshing effect. The commonly used preparation is caffeine sodium (caffeine benzoate), which is a central stimulant and can strengthen the excitement process of cerebral cortex. It is used for neurasthenia and depression, and compound paracetamol tablets are prepared as medical devices.
Extraction process
Traditional methods for preparing tea polyphenols from tea mainly fall into the following three categories.
Solvent extraction method
Soak tea leaves in polar solvent, then carry out liquid-liquid extraction and separation, and finally concentrate to obtain the product. At present, this method is mainly used in industrial production. The product yield is 5%~ 10%, and the product purity is 80%~98%. The solvents used are acetone, ether, methanol, hexane and chloroform. This method has high production cost and is easy to cause pollution.
Ion precipitation method
Tea polyphenols are precipitated by metal and separated from caffeine. This method uses heavy metals toxic to human body as precipitant, so the products produced by this method are difficult to meet the requirements of food and pharmaceutical industries.
Column separation preparation method
Gel column, adsorption column and ion exchange column method. The key of this technology is column packing and leaching. The results show that the yield of tea polyphenols is between 4% and 8% and the purity can reach 98% by column separation preparation method, but the column packing is very expensive and needs a variety of organic solvents to elute, which is obviously not suitable for industrial production. There are some problems and shortcomings in the above traditional methods, and the products can not meet the requirements of food additives and pharmaceutical industry in terms of safety, price and purity. In order to solve these problems, through repeated experiments by relevant experts, a new process of preparing high-purity tea polyphenols by combining supercritical CO2 extraction technology with traditional extraction, concentration and extraction technology was successfully developed. This process not only improves the purity and yield of tea polyphenols. It also meets the requirements of industrial production on raw materials, solvent use, production route, production process safety, product color, yield and purity, and is beneficial to the more effective application of tea polyphenols in medicine and food industry.
Content determination
principle
Tea polyphenols in tea can form purple-blue complexes with ferrous ions. Its content was determined by spectrophotometry.
Instruments and appliances
Conventional laboratory instruments and the following items: analytical balance: sensitivity 0.0001g. Spectrophotometer
Reagents and solutions
The reagent used should be analytically pure (AR) and the water should be distilled water.
1 ferrous tartrate solution: weigh 1g (accurate to 0.000 1g) ferrous sulfate and 5g (accurate to 0.000 1g) potassium sodium tartrate, dissolve in water, and fix the volume to 1L (the solution should be protected from light.
2 pH7.5 phosphate buffer: dipotassium hydrogen phosphate: weigh 23.377g dipotassium hydrogen phosphate, add water to dissolve it, and make it constant to1l. Potassium dihydrogen phosphate: weigh 9.078g of potassium dihydrogen phosphate, add water to dissolve it, and fix the volume to1l. Take 85ml of the above dipotassium phosphate solution and15ml of potassium dihydrogen phosphate solution, and mix them evenly.
operational approach
1 sampling shall be carried out according to tea sampling regulations.
2 Sample preparation The sample was prepared according to the provisions of "Preparation of Tea Pulverized Sample and Determination of Dry Matter Content".
3 Determination step (1) Preparation of test solution Prepare the test solution according to the regulations in the determination of tea extract. (2) Accurately suck 1ml of the above (1) test solution, inject it into a 25mL volumetric flask, add 4mL of water and 5mL of ferrous tartrate solution, fully mix them, add a buffer with pH of pH7.5 to the scale, use a 10mm colorimetric cup, and measure the absorbance (A) at the wavelength of 540nm with reference to the reagent blank solution. 5. Calculation method and formula: The content of tea polyphenols in tea is expressed as dry mass percentage and calculated according to the following formula: tea polyphenols (%) = (a×1.957× 2)/100× l1(L2× m× m), where: l65438. L2—— the amount of liquid used in the determination, milliliter (ml); M—— mass of sample, g; M—— percentage of dry matter content of the sample,%; A- absorbance of the sample; 1.957—— Use a 10mm cuvette. When the absorbance is equal to 0.50, each milliliter of tea soup contains tea polyphenols equivalent to1.957mg. If the repeatability requirements are met, take the arithmetic average of the two determinations as the result. In every 100g sample, the difference between two measured values of the same sample with repeatability shall not exceed 0.5g.
Application prospect
Tea polyphenols have strong oxidation resistance and physiological activity, and are scavengers of human free radicals. According to the research of relevant departments, the efficacy of 1 mg tea polyphenols in scavenging excessive free radicals harmful to human body is equivalent to 9 μ g superoxide dismutase (SOD), which is much higher than other similar substances. Tea polyphenols can block lipid peroxidation and remove active enzymes. According to the test results of Tomoyo in Ota, Japan, it is confirmed that the anti-aging effect of tea polyphenols is 18 times stronger than that of vitamin E.
Helps to inhibit cardiovascular diseases.
Tea polyphenols play an important role in human fat metabolism. The human body has cardiovascular diseases such as high cholesterol and triglycerides, such as fat deposition on the inner wall of blood vessels and atherosclerotic plaques formed after vascular smooth muscle cells proliferate. Tea polyphenols, especially catechins ECG and EGC in tea polyphenols and its oxidation products theaflavins, are helpful to inhibit this mottled proliferation, reduce the formation of fibrinogen that enhances coagulation viscosity, make coagulation clear, and thus inhibit atherosclerosis.
Helps prevent and fight cancer.
Tea polyphenols can block the synthesis of carcinogens such as nitrite in the body, which can directly kill cancer cells and improve the immune ability of the body. According to relevant data, tea polyphenols (mainly catechins) in tea are beneficial to the prevention and adjuvant treatment of cancers such as gastric cancer and intestinal cancer.
It is helpful to prevent and treat radiation injury.
Tea polyphenols and their oxidation products have the ability to absorb the toxicity of radioactive substances strontium 90 and cobalt 60. According to the clinical trials of relevant medical departments, the treatment of mild radiation sickness caused by radiotherapy with tea extract can reach more than 90%. For cytopenia, the effective rate of tea extract is 865438 0.7%; It has a good therapeutic effect on leukopenia caused by radiation.
Helps to inhibit and resist viruses and bacteria.
Tea polyphenols have strong convergence, obvious inhibition and killing effects on pathogenic bacteria and viruses, and obvious anti-inflammatory and antidiarrheal effects. Many medical units in China use tea preparations to treat acute and chronic diseases and amebiasis, and the cure rate is about 90%.
Conducive to beauty and skin care
Tea polyphenols are water-soluble substances, which can remove greasy face and astringe pores, and have the effects of disinfection, sterilization, anti-aging and reducing the damage of ultraviolet rays in the sun to the skin.
Help to refresh yourself.
Caffeine in tea can stimulate the central nervous system of human body, enhance the excitement process of cerebral cortex, and has the functions of refreshing the brain, clearing away heart fire and calming the nerves.
Helps diuresis and relieve fatigue.
Caffeine in tea can stimulate the kidney, promote the rapid excretion of urine, improve the filtration rate of the kidney and reduce the retention time of harmful substances in the kidney. Caffeine can also eliminate excessive lactic acid in urine, which helps to eliminate fatigue as soon as possible.
Helps to lower blood fat and help digestion.
It is recorded in the Tang Dynasty that the effect of tea is "eating for a long time makes you thin". There is a saying among the ethnic minorities in China's border areas that "tea is indispensable for a day". Because tea helps digestion and reduce fat, in today's fashionable language, it is helpful to "lose weight". This is because caffeine in tea can increase the secretion of gastric juice, help digestion and enhance the ability to decompose fat. The so-called "long-term eating makes people thin" is here.
Helps protect teeth and improve eyesight.
The fluorine content in tea is high, and the fluorine content per 100 g of dry tea is 100 mg ~ 15 mg, of which 80% is water soluble. If everyone drinks 10g tea every day, they can absorb 1mg ~ 1.5mg of water-soluble fluoride. Moreover, tea is an alkaline beverage, which can inhibit the reduction of calcium in the human body, help prevent dental caries, protect teeth and strengthen teeth. According to relevant data, the experiment of "gargling with tea after meals" among primary school students can reduce the incidence of dental caries by 80%. According to the investigation of relevant medical units, 28.6% of cataract patients have the habit of drinking tea, and 7 1.4% have no habit of drinking tea. This is because vitamin C and other ingredients in tea can reduce the turbidity of eyes, and drinking tea often has a positive effect on reducing eye diseases, protecting eyes and improving vision.