With the deepening of scientists' research on free radicals, the methods of eliminating free radicals to reduce the harm of free radicals to human body are gradually revealed.
Studies show that the process of free radicals from generation to decay is the process of electron transfer. In the life system, the transfer of electrons is the most basic movement, and oxygen is the most easy element to get electrons. Therefore, many chemical reactions in organisms are related to oxygen. Scientists have found that almost all free radicals harmful to human health are related to those oxygen-containing substances with strong activity. They call the free radicals combined with these substances active oxygen free radicals. The harm of reactive oxygen species to human body is actually an oxidation process. Therefore, in order to reduce the damage of free radicals, we must start with anti-oxidation.
Because free radicals not only exist in human body, but also come from human body, there are two ways to reduce the harm of free radicals: one is to use endogenous free radical scavenging system to remove excess free radicals in the body; The second is to explore the exogenous antioxidant-free radical scavenger to block the damage of free radicals to human body.
A large number of studies have confirmed that the human body has the ability to scavenge excessive free radicals, which mainly depends on endogenous free radical scavenging systems, including some enzymes such as superoxide dismutase (SOD), catalase and glutathione peroxidase, as well as some antioxidants such as vitamin C, vitamin E, reduced glutathione, β-carotene and selenium. Enzymes can turn active oxygen free radicals in the body into substances with low activity, thus weakening their attacks on the body. The defensive function of enzymes is limited to cells. Some antioxidants act on cell membranes, while others can play a defensive role outside cells. These substances are deeply hidden in our bodies. As long as their quantity and vitality are maintained, they will exert their ability to scavenge excess free radicals and keep the free radicals in our body in balance.
In order to reduce the harm of free radicals to human body, we should not only rely on the free radical scavenging system in vivo, but also seek and explore exogenous free radical scavengers, and use these substances as body body double, so that they can combine with free radicals before entering human body, thus blocking the attack of external free radicals and protecting human body from harm.
In nature, there are many kinds of antioxidants that can act on free radicals. At present, many valuable natural antioxidants have been found at home and abroad. In this research, China scientists have been at the forefront of the world. They found and proved that some unique edible and medicinal plants in China contain a large number of phenolic substances, which are characterized by the fact that electrons are easily carried away by free radicals, and after losing electrons, they will become stable substances that are harmless to people.
Experts from Institute of Biophysics, Chinese Academy of Sciences have developed a natural antioxidant-free radical scavenger formula from these plants after eight years. In the animal acute toxicity experiment cooperated with technicians from Beijing Cigarette Factory, it was proved that the life span of mice using free radical scavenger was significantly longer than that of mice not using free radical scavenger, and the longest life span could even be nearly doubled, and the gene canceration rate was greatly reduced.
At present, the free radical scavenger of smoking smoke has been applied to Zhongnanhai brand 5 mg low tar and low free radical cigarettes. This indicates that China has been at the international leading level in the application of cigarette free radical scavengers. International tobacco experts believe that this is a cross-century contribution to the study of smoking and health in the world.
This achievement is consistent with China's traditional view that medicine, food and medicine are of the same origin. It is a characteristic of China to develop free radical scavengers from Chinese herbal medicines and foods. Researchers in China are making full use of the advantages of traditional pharmacy to find more efficient and nontoxic free radical scavengers and apply them to food, medicine, cosmetics and other fields for the benefit of the people.
Of course, if human beings want to fundamentally avoid the infringement of redundant free radicals, they should also strengthen their awareness of environmental protection and effectively improve our living environment.
free radical
A free radical is a molecule or part of a molecule that can exist independently and contains one or more unpaired electrons. Because free radicals contain unpaired electrons, they tend to pair. Therefore, most free radicals are very active and have high chemical activity. In the process of free radical pairing reaction, new free radicals will be formed. Under normal circumstances, free radicals in the human body are in a dynamic balance of continuous production and elimination. Free radicals are an effective defense system of the body. If we can't maintain a certain level of free radicals, it will bring adverse effects to the life activities of the body. However, the excessive production or removal of free radicals is slow, which will cause various damages to the body at the molecular level, the cellular level and the tissue and organ level by attacking living macromolecules and various cells, accelerate the aging process of the body and induce various diseases.
Causes of excessive production of free radicals
1, abnormal human metabolites 2, exposure to toxic chemicals 3, drugs, smoking, alcoholism 4, long-term sun exposure 5, long-term living in anoxic/anoxic environment 6, environmental pollution factors 7, excessive exercise 8, diseases 9, unhealthy eating habits (overnutrition and excessive fat intake) 10, radiation pollution1.
Damage of free radicals to life macromolecules
Due to the high activity of free radicals and strong oxidation reaction ability, they can attack any molecules they meet through oxidation, so that macromolecules in the body are denatured, cross-linked or broken, thus causing the destruction of cell structure and function, leading to tissue damage and organ degradation.
The action of free radicals on nucleic acids will cause a series of chemical changes, such as the removal of amino or hydroxyl groups, the breaking of the connecting bond between base and ribose, the oxidation of ribose, the breaking of phosphate bond and so on.
The study of ionizing radiation-induced free radicals in vivo water environment shows that high dose radiation can directly break DNA, while low dose radiation can break DNA backbone.
★ The harm of free radicals to protein
Free radicals can directly act on protein or indirectly destroy protein through lipid peroxide products.
★ Harm of free radicals to sugars
Free radicals destroy polysaccharides through oxidative degradation, such as affecting polysaccharides in cerebrospinal fluid, thus affecting the normal function of the brain. Free radicals make ribose and deoxyribose form dehydrogenation free radicals, which leads to the breakage of DNA main chain or base damage, and can also oxidize the hydroxyl groups of sugar molecules in cell membrane oligosaccharide chains to form unsaturated carbonyl groups or polymerize into dimers, thus destroying the polysaccharide structure on cell membrane and affecting the play of cellular immune function.
★ Damage of free radicals to lipids
Polyunsaturated fatty acids in lipids are chemically active because they contain multiple double bonds, and are most vulnerable to free radicals and oxidation reactions. Phosphatidyl is an important part of biofilm, which is easily destroyed by free radicals because it is rich in polyunsaturated fatty acids. This will seriously affect the various physiological functions of the membrane, and free radicals will seriously damage the biofilm tissue and cause great disorder of cell function.
Free radicals and diseases
(a) free radicals and aging
Since ancient times, people have put forward more than 300 aging theories according to different understandings of aging mechanism. Free radical theory is one of them. Part of the mechanism that reflects the essence of aging.
Harman in England first proposed that free radicals are related to aging and diseases in 1956, and then published the first research report in 1957, pointing out that feeding mice with 0.5%- 1% free radical scavenger can prolong their life. Because the free radical theory can clearly explain various symptoms in the aging process, such as senile plaque, wrinkles, decreased immunity, etc., it has attracted much attention and been widely accepted by people. The central content of free radical aging theory holds that aging comes from the randomness and destructive effect of free radicals produced in the normal metabolism of the body, and the main mechanism of free radicals causing aging of the body can be summarized as follows.
1. Cross-linking polymerization of living macromolecules and accumulation of brown pigment.
Free radicals act on lipid peroxidation, and malondialdehyde, the final product of oxidation, will cause cross-linking polymerization of life macromolecules such as protein and nucleic acid, which is a basic factor of aging. Lipoprotein is insoluble in water, so it is not easy to be eliminated. In this way, it accumulates in a large number of cells and skin cells, that is, senile plaques are formed, which is an external sign of aging. When skin cells accumulate, there will be memory loss or mental retardation or even Alzheimer's disease. Cross-linking and polymerization of collagen will reduce the solubility, elasticity and hydration ability of collagen, resulting in skin tension loss, increased wrinkles and weakened bone regeneration ability of the elderly. Lipid peroxidation leads to blurred retina and other pathological changes of eyeball lens, which induces visual impairment (such as dizziness and cataract) in the elderly.
Skin aging and wrinkles are caused by the destruction of free radicals. The accumulation of lipofuscin reduces the immunity of skin cells and increases the susceptibility of skin tumors. These are the destruction of free radicals.
2. Destruction and reduction of organs, tissues and cells
The destruction and reduction of organs, tissues and cells is one of the symptoms of aging. For example, the obvious decrease in the number of neurons is another important reason for the decline of sensory and memory ability, slow action and mental retardation of the elderly. The destruction or reduction of organs, tissues and cells is mainly due to gene mutation which changes the transmission of genetic information, leading to the wrong synthesis of protein and enzymes and the decrease of enzyme activity. The accumulation of these substances leads to the aging and death of organs, tissues and cells. Unsaturated fatty acids on biofilm are easily attacked by free radicals and undergo peroxidation. Oxidation has an important influence on aging, and free radicals accelerate the aging process of cells by attacking lipids.
3. Decreased immune function.
Free radicals act on the immune system, or on lymphocytes to damage them, which weakens the cellular immunity and humoral immunity of the elderly, reduces the ability of immune recognition and leads to autoimmune diseases.
The so-called autoimmune disease means that the immune system not only attacks pathogens and abnormal cells, but also invades their normal healthy tissues and attacks their own tissues as foreign bodies. Autoimmune diseases such as diffuse scleroderma, systemic induration, ulcerative colitis, gliosis and Crohn's disease (local ileitis) are often accompanied by more chromosome breaks. Studies have shown that the pathological process of autoimmune diseases is closely related to free radicals.
(2) Free radicals and cancer
For a long time, people have been committed to exploring the causes of cancer from different angles. Since the discovery that highly active free radicals can cause a rapidly expanding chain reaction, people have linked the rapid growth of these properties and studied the participation of free radicals in various carcinogenesis processes. The current view is that many carcinogens must undergo metabolic activation to form free radicals, and attack DNA to cause cancer. Many anticancer agents also kill cancer cells through free radical formation.
A normal cell must go through two stages: induction and promotion, which is the two-step canceration theory. There are many attractants in nature, such as croton oil, croton oil, cigarette smoke condensate, unburned tobacco extract, surfactants such as sodium dodecyl sulfate and tween 60, fatty acid methyl esters, phenols, straight-chain alkanes and so on.
The induction stage is closely related to free radicals.
Peroxide products produced by free radicals acting on lipids can cause cancer and mutation, and the mechanism of cancer and mutation is the same at the molecular level.
The stage of promoting cancer is also related to free radicals, and the ability of promoting cancer is parallel to its ability to produce free radicals.
In the process of chemotherapy, due to the toxicity of drugs, a large number of free radicals are produced in cells, which often leads to bone marrow damage and leukopenia, which leads to the slowdown of chemotherapy, the reduction of dose or the forced cessation of chemotherapy. If free radical scavenger is used, it can prevent further damage of oxygen free radicals to bone marrow, accelerate the recovery of bone marrow and white blood cell count, and be beneficial to the continuation of chemotherapy.
(3) Free radicals and reperfusion injury after ischemia
Tissue damage caused by ischemia is the main cause of fatal diseases, such as coronary atherosclerosis and stroke. However, there is a lot of evidence that simple ischemia is not enough to cause tissue damage, and only when blood supply is suddenly restored after ischemia for a period of time (that is, reperfusion) can tissue damage be caused. The damage of microvascular and parenchymal organs caused by ischemia reperfusion is mainly caused by reactive oxygen species, which has been confirmed in many organs. Traumatic shock, surgery, organ transplantation, burns, frostbite and thrombosis will all cause ischemia-reperfusion injury.
In ischemic tissue, the synthetic ability of antioxidant enzymes that can scavenge free radicals is impaired, which aggravates the damage of free radicals to reperfusion tissue after ischemia. The free radical scavenger of grape seed extract has protective effect on ischemia-reperfusion tissue injury.
Free radicals and emphysema
Emphysema is characterized by the destruction of bronchioles and alveolar ducts, the decrease of alveolar septum area and the decrease of gas exchange between blood and lungs. These pathological changes are due to the attack of free radicals on lung macrophages and the release of proteolytic enzymes (such as elastase), which lead to the damage and destruction of lung tissue.
Smoking is easy to cause emphysema because cigarette smoke induces the aggregation and activation of pulmonary macrophages. The proteolytic activity of neutrophils in the bronchoalveolar eluate of smokers is higher than that of non-smokers, and the O2 content produced by leukocytes in the eluate is much higher than that of non-smokers. Therefore, cigarettes and other pollutants can induce emphysema.
(5) Free radicals and eye diseases
Eyes are the only photoreceptors of human beings and animals, and senile eye aging (especially cataract) is related to free radical reaction. Studies have shown that due to the aging of the elderly, the content and activity of free radical scavengers in eyeball lens decrease, which leads to the decline of the ability to resist free radical invasion. Facts show that the occurrence and development of cataract is related to the damage of free radicals to retina and the destruction of lens tissue.
Free radical attack on cornea leads to endothelial cell rupture, cell permeability dysfunction and corneal edema. Free radicals can directly damage the lens of the eye.
(vi) Free radicals and inflammation
Regarding the mechanism of inflammation, some people think that local hypoxia or some foreign substances (including pathogenic bacteria and energy) cause the release of lysosomal enzymes and cause cell death, and these white blood cells are activated by special metabolic stimuli. On the one hand, free radicals destroy pathogenic bacteria and diseased cells, on the other hand, they attack white blood cells themselves, causing a large number of deaths. As a result, lysosomal enzymes are released in large quantities, further killing or killing tissues and cells, leading to the destruction of bones and cartilage, leading to inflammation and arthritis.
It can be seen that the inflammatory process is closely related to this. Some scientists believe that the cause of arthritis induced by free radicals is the degradation of hyaluronic acid, because hyaluronic acid is the main component of high-viscosity joint lubricating fluid.
(vii) Free radicals and other diseases
Free radicals attack unsaturated fatty acids in arterial wall and serum to make them undergo oxidation reaction and generate lipid peroxide, which can stimulate arterial wall and increase the trend of atherosclerosis. The degree of atherosclerosis is positively correlated with the degree of lipid peroxidation in atherosclerotic plaques, and the wax-like substance on the inner wall of blood vessels is a direct proof of lipid peroxidation. Atherosclerosis is aggravated with age, which is directly related to the high content of unsaturated fatty acids in arterial wall and the high content of Fe2 ++ and Cu2 ++ in serum of the elderly. Malondialdehyde peroxide promotes the cross-linking of elastin, destroys its normal structure and function, loses its elasticity and water-retaining ability, and finally leads to arteriosclerosis, which further induces other cardiovascular diseases such as coronary heart disease. The relationship between free radicals and diabetes is very complicated. It is known that free radicals can protect alloxan-induced insulin-dependent diabetes, but the role of free radicals in inducing other types of diabetes is not clear.
The above process can lead to a series of anemia and hemolysis. Free radicals also participate in the pathological process of iron deficiency anemia.
Kaschin-Beck disease and Keshan disease are two terrible endemic diseases, which are distributed in the low selenium belt from northeast to southwest of China. The former shows symptoms such as bone marrow injury, short foot deformity, short stature and lack of labor force, while the latter shows symptoms such as myocardial necrosis and cardiac insufficiency. At the subcellular level, both diseases show the damage of membrane system. The composition and function of phospholipids in myocardial mitochondrial membrane, serosa, chondrocytes and erythrocyte membrane have changed, and they participate in free radicals at the molecular level, which is closely related to the free radical reaction in vivo.
Free radicals can cause damage to biofilm and other tissues. The accumulated free radicals will lead to a series of pathological processes such as aging.
In the long-term evolution process, organisms will inevitably produce some substances that can scavenge these free radicals, which are collectively called free radical scavengers.
However, with the increase of age, especially the rapid changes of living environment and social environment, the ability of most people to produce free radical scavengers gradually decreases, which leads to the decrease of the content and activity of scavengers in the body, thus weakening the defense ability against free radical damage, accelerating life aging and triggering a series of pathological changes. In order to prevent the destruction of free radicals, some free radical scavengers can be added to the living body, so as to achieve the purpose of resisting diseases and delaying aging.
Natural antioxidant
Humans are attacked by free radicals thousands of times every day. Therefore, since 1950s, scientists have devoted themselves to building a defense line against free radical oxidation and anti-aging in human body. This is to make the antioxidant give an electron to the free radical without forming harmful and dangerous substances that can cause chain reaction, so that the oxygen free radical is neutralized and the harmful chain reaction is terminated. The research on how antioxidants can eliminate free radicals and play an antioxidant role in human body has occupied an important position in the field of medical care in the new century. People pay more and more attention to antioxidant products with the function of scavenging free radicals. Well-known antioxidants in vivo include vitamin E, vitamin C, β-carotene, superoxide dismutase (SOD) and glutathione. In addition, many substances have been proved to have antioxidant effects, such as flavonoids, saponins, tea polyphenols, phospholipids, lecithin and trace elements such as selenium and germanium. There are also many synthetic chemicals that have antioxidant effects. These products are mixed, and some synthetic products have certain toxicity. Under the tide of green health care returning to nature, it is an inevitable choice for people to extract non-toxic and safe antioxidant active substances from natural substances.
Nutritionists have long advocated eating more fresh fruits and vegetables to prevent diseases. The scientific truth is that it contains a lot of antioxidant substances such as vitamin C, β-carotene and flavonoids. In fact, the antioxidants we take in from our daily diet often can't meet our body's needs. Pre-anthocyanin with strong antioxidant effect is high in plant skin, seed core and wood essence. Because of the potential danger of pesticide, chemical ripening agent and other residues in fruit skin, as well as taste factors, these parts are often abandoned by people. Although fresh fruits and vegetables are rich in antioxidant substances such as vitamin C and β-carotene, the antioxidant activity of food will decrease or even disappear during cooking. Even if you eat fresh fruits and vegetables five times a day, the antioxidants in your body are still not enough, especially when you are under pressure, air pollution or smoking, and more free radicals are produced in your body, so you need to supplement antioxidant substances.
Antioxidant effect of polyphenol compounds
Polyphenols are important non-nutritional components in diet, including phenolic acids, flavonoids, lignans, coumarins and tannins. Modern science is very active in the study of proanthocyanidins and anthocyanins. Proanthocyanidins are larger molecules in polyphenols, also known as tannins, which exist in some grains and fruits. The purpose of the earliest research is its anti-nutritional performance, which can form water-insoluble complexes with protein and digestive enzymes, affecting the digestion and absorption of food. Anthocyanin is the source of red, blue and purple in most plant varieties.
Recently, there have been many studies on the antioxidant effect of proanthocyanidins, which have proved that proanthocyanidins can scavenge free radicals in the body and reduce lipid peroxidation. Protect cell membrane and DNA from oxidative damage, interfere with the combination of hormones and cells, complex metals and induce enzymes that change carcinogenicity; Anti-mutation and anti-cancer effects; Inhibit platelet aggregation and diminish inflammation; Anti-allergic; Anti-aging.
The proanthocyanidins (OPC, OPCs, PCO) in grape seed extract are a mixture of various proanthocyanidins with low polymerization degree, and their structures are as follows:
Procyanidins are precursors of anthocyanins, which can be transformed into anthocyanins in plants. Reacting with inorganic acids can also be converted into anthocyanins. Anthocyanin has a wide spectrum, which can bring bright colors to food and increase appetite. Some physiological functions are similar to procyanidins. An important application example of proanthocyanidins is blueberry (blueberry, indigo) extract, which is used as health food in Europe to protect and improve eyesight.