Posted By; Raaz K Maheshwari, Karuna Mittal, Bina Rani
- Department of Chemistry, MDSU’s Govt PG College, Nagaur, Rajasthan
- Research at University of Rochester Medical Centre, Peachtree Dunwoody Road Sandy Springs Geogea
- Department of Engineering Chemistry ^& Environmental engineering, PCE, Sitapura, Jaipur, Rajasthan
Antioxidants are vitamins or nutrients that may help to prevent the damaging effects of oxidation on your body’s organs and tissues. They achieve this by protecting the cells of human body from the damage done by “free radicals”. Protection of body cells is the main feature and root cause for all benefits of antioxidants. What are free radicals, and how do they damage cells? From the name “Anti-oxidant” you can see that the function of these nutrients is somehow in their opposition to oxidation. You might guess that the benefits of antioxidants are somehow related to “fighting” oxidation as if it were a bad thing…
Well, here is the situation. The oxidation process can be described as the “flame of life”. Oxidation is the change in a chemical when its atoms lose their electrons. This process constantly occurs in order to produce energy within our body. The natural by-products of this process are free radicals: atoms which lack electrons. These free radicals cause aging and other complications. The older we become, the larger the amount of free radicals which may be accumulated in our bodies – and the possibility of resultant cell damage becomes more severe. Free radicals are reactive chemical species that differ from other compounds in that they have unpaired electrons in their outer orbitals. They are capable of damaging cellular components, and accumulating evidence suggests they may contribute to various disease entities. Biologic systems are exposed to free radicals that have been formed endogenously or that result from external influences such as ionizing radiation. Oxygen free radicals are continuously being produced intracellularly by oxidation-reduction reactions. The sequential univalent reduction of molecular oxygen initially forms the superoxide anion radical, which in turn is converted, in the presence of transition metal ions, into the highly reactive hydroxyl radical. Free radicals are detected by electron spin resonance spectroscopy, but often this procedure is difficult to use for study of free radical involvement in biologic systems, and investigators have resorted to inferring their presence by identifying the products of free radical reactions. All aerobic organisms possess substances that help prevent free radical-mediated injury. These include antioxidants such as vitamin E and the enzymes superoxide dismutase and glutathione peroxidase. Free radicals damage cells and cell membranes because they “steal” electrons from cell molecules. This change may result in a chain reaction, in which more and more molecules will lose their electrons. This makes the whole cell work in a “wrong” way – and this is what may cause a disease! Of course, just one single cell would not make much of difference to anyone’s health. Many cells would need to be damaged before any symptoms will appear. There are many factors in our environment which contribute to an increase of free radicals in our bodies.
External damaging free radicals are derived from the elements we live with, such as chlorine in the water we drink, chemicals in the food we eat, smoking, polluted air we breathe and radiation from the sun or other sources like power lines, electromagnetic waves etc. Free radicals can steal an electron and break down another biomolecule such as loose proteins, sugars, fatty acids, etc. that are not part of a larger chemical structure. In these cases the free radical does little damage. If a free radical steals an electron from one of the proteins that is contained in a strand of collagen (rather than a loose protein), it causes a change in the chemical structure of the collagen at that point and causes a break in the collagen strand. This is damage. Once a bundle of collagen has multiple points of damage which occurs over years, the strand of collagen becomes dysfunctional and loses its elastic quality6. The skin begins to sag. Over time free radical damage happens to the various components of the body and this damage is progressive. Free radicals chip away at cell walls, molecule by molecule, making holes. The cells leak and lose their chemical balances. Subsequent free radicals are able to chip away at DNA, making cells dysfunctional. If this damage affects cellular DNA, the cell may malfunction and this is what happens cell by cell over the lifetime of a human being, ultimately causing entire organs to malfunction, because their cells malfunction. If the DNA of basal keratinocytes, for example, are damaged the cells may become dysfunctional and the basal cells will reproduce cells that are equally as damaged and dysfunctional, resulting in the aging and dysfunction of the skin and its various components. Aging is simply the progression of damage, caused by free radicals.
The major creators of free radicals in the skin are (1. normal chemical processes such as producing and using energy, producing skin components such as lipids, and other daily chemical processes that give off free radicals as a natural byproduct (2. unprotected sun exposure, (3. products applied to the skin that produce free radicals and (4. pollution. When acne is involved, acne becomes another creator of free radicals and in the case of moderate to severe acne, assumes the second position, ahead of unprotected sun exposure. Most of the chemical processes that occur in the skin, emit free radicals. In the body, the processing of food, producing energy and using energy creates free radicals. Breathing and using our muscles to perform functions creates free radicals. Manufacturing collagen or lipids or pigment produces free radicals. These free radicals can create damage to the components of the skin as they steal an electron from another component to make themselves complete and stable. When acne infections occur, the skin generates hydrogen peroxide to kill bacteria. Hydrogen peroxide gives peroxide free radical and damages the components of the skin. The infections destroy skin components and all of these components must be repaired or reproduced. This again generates volumes of chemical processes that generate additional volumes of damaging free radicals.
One way to protect cells from free radicals is to provide our bodies with molecules which can be used as targets for oxidation – diverting their “attention” from the molecules that make cells and membranes! These special molecules are antioxidants: they are able easily to lose, or to accept electrons, with no harm done.
So, the major feature of antioxidants is that they neutralize free radicals, thus preventing potential damage. All the benefits of antioxidants are the result of this feature. Antioxidants are molecules which can safely interact with free radicals and terminate the chain reaction before vital molecules are damaged.
Carotenoids: Terpenes are the largest class of phytochemicals, with carotenoids and limonoids being its two major subclasses. There are more than 700 naturally occurring carotenoids that acts as biological antioxidants and protect cells and tissues from the damaging effects of free radicals. Carrots, tomatoes, parsley, papaya, orange and green leafy vegetables like amaranth, chenopods, mustard, fenugreek, spinach, cabbage, radish and turnip are rich sources of carotenoids. They have been classified into two major groups on the basis of their structure (i) carotenes (β-carotene, lycopene) containing only carbon and hydrogen that may be cyclic or linear; and (ii) oxycarotenoids (xanthophylls, lutein) containing carbon, hydrogen and oxygen in the form of hydroxyl, epoxy or oxy groups. In carotenoids, the polyene chain with conjugated double bonds is responsible for their characteristic absorption spectra and specific photochemical properties. Among the carotenes, natural β-carotene is the precursor of vitamin A and has preventive action against eye diseases and cancer. Carotenes enhance immune response and protect skin cells against UV radiations. They help to lower the risk of cardiovascular diseases, age related vision disorders, asthma and reduce inflammation. Lycopene in red coloured tomatoes is effective against oxidative stress.. Along with carotene and lutein, it provides protection against lung, breast, uterus and prostate cancers. Green leafy vegetables and corn are best sources of xanthophylls and protect retinal part of human eye. Astaxanthin, a xanthophylls found in sea foods, and limonoids present in citrus fruits are biologically active phytochemicals which protect lung tissue from free oxygen radicals and inhibit proliferation of human breast cancer.
Tocopherols and Tocotrienols: They are non-polar constituents of biological membranes that exist in nature of lipid phase. Vitamin E is found in unrefined cereal grain, vegetable oils, wheat germ, nuts, fruits and green leafy vegetables and have beneficial effects in heart, cancer, cataract, and Alzheimer’s disease. α-tocopherol is the most abundant forms of tocopherols. γ-tocopherols can reduce most effectively the concentration of nitrogen dioxide that is involved in carcinogenesis, arthritis, and neurologic diseases. The unique structure of α-tocopherol enables it to act as an effective antioxidant and to be regenerated through reaction with other oxidants. Tocopherols, mainly found in palm oil, cereal grains and kale are potential antioxidants and are associated with the reduced risk of cancer, Alzheimer’s and cardiovascular diseases. They also have cholesterol lowering ability and inhibit LDL (Low Density Lipoprotein) oxidation. α-tocopherol is preferentially absorbed compared to its other forms. Even though tocotrienols have a higher radical scavenging activity than tocopherols, they are less bio-available as compared to the latter.
Ascorbic acid (Vitamin C): Rose hips, chillies, guava, citrus fruits, berries, kiwi fruit and some vegetables are main sources of vitamin C with beneficial effects in cardiovascular health, cancer, immunity and connective tissues. It is leading natural antioxidant that can scavenge ROS and has anticarcinogenic effect. It is excellent electron donor, which makes generation of relatively stable semidehydroascorbic acid as well as its easy conversion from dehydroascorbic acid to ascorbic acid possible. Synthetic antioxidants such as BHT and BHA were found less effective than ascorbic acid. Oxidation of ascorbic acid is highly influenced by heat, light, water, pH, oxygen concentration and metal ions like Cu+2 and Fe+3. It may be related to the prevention of some forms of cancer and heart diseases. Ascorbic acid and tocopherol supplementation can substantially reduce oxidative damage. Their effects are greater in non-smokers than smokers. Smoking induces oxidative stress from numerous free radical compounds in the gaseous phase and the radicals formed from ascorbic acid acts as pro-oxidant in smokers.
Lipoic acid: Some sulphur containing compounds like GSH [glutathione], lipoic acid and dihydro liopic acid present in spinach, broccoli and yeast show antioxidant activities. They prevent oxidative damage of proteins, regenerate GSH in the liver, kidney and lung tissues, protect brain and nerve tissues, and reduce diabetes related complications and thus play an important role in reduction of blood glucose concentration. Lipoic acid improves mitochondrial membrane potential. Age related memory loss and brain ailments, including Alzheimer’s and Parkinson’s disease. It also has the ability for radical scavenging and metal chelation.
Polyphenols: The term polyphenol or phenolics refer precisely to those chemical compounds which have an aromatic ring with hydroxyl substituent (s)., including their derivatives. On the basis of chemical structure, they can be classified into phenolic acids, flavonoids, stibenes and lignans. Berries, ginkago, onions, apples grapes, chamomile, dandelion, green tea , hawthorn, licorice, rosemary, thyme, and some beverages (like red wine, coffee, cocoa, beer) are natural sources of polyphenols with strong antioxidant activity and biological properties. They can enhance the activity of vitamin C. they act against allergies, ulcers, tumours, platelet aggregation, are and are also effective in controlling hyper tension. Flavonoids possess ideal structure for free radical scavenging activity and have been found to be more effective antioxidant in vitro than tocopherols and ascorbates. More than 4,000 flavonoids have been identified in plants, which are responsible for the colour of vegetables, fruits, grains, seeds, leaves, flowers, bark and product derived from them. They are powerful antioxidant that inhibit the oxidation of low density lipoprotein (LDL), a major factor in the promotion of atherosclerosis, which is the plaque build-up in arteries that can lead to heart attack or stroke. Isoflavones like genestein and daidzein found abundantly in legumes such as lentils, chickpeas and soyabeans, have neutraceutical properties against tumour growth and cancer and they form one of the main classes of oestrogenic substances in plants.
Polyphenols are powerful scavengers of free radicals and also act as anti-inflammatory, anti-ulcer, antitumour and anticancer agents. They act as potent chain-breaking antioxidants and possess vitamin C stabilising activity by increasing its adsorption. Their therapeutic usefulness has been demonstrated in gastrointestinal haemorrhages, radiation reactions, erythroblastosis, menorrhagia, bleeding cystilis, tuberculosis, haemophysis, periodontal diseases, epitasis, and ophthalmic disorders. Polyphenols bind with transition metals, particularly iron and copper, and thus inhibit transition metal-catalysed free-radical formation. The chelated transition metals become unavailable to interact with other compounds and initiate biologically damaging reactions. Polyphenols inhibit lipid peroxidation, oxidation of linoleic acid and Fe+2 catalysed oxidation of glutamine synthase, through free radical scavenging and removal of metals ions from catalytic sites via chelation. They are also known to modify the activities of some enzymes involved in immune functions, carcinogenesis, cellular transformations, tumour growth and metastasis. Biological effects of phenols are of great interest since evidence has been found that they offer protection against several diseases. They have the potential to inhibit oxidation of LDL that is considered to be a key mechanism in atherosclerosis. Certain studies have shown that the consumption of foods rich in polyphenols results in reduced susceptibility of LDL to oxidation and are also effective scavengers of free radicals, responsible for DNA damage and tumour promotion. They were found to have beneficial effect in rheumatoid arthritis and experimental studies showed their anti-inflammatory activity.
Epidemiological studies provide convincing evidence that a diet rich in antioxidant is associated with a lower incidence of degenerative diseases. Cereals, legumes (barley, corn, nuts, oats, rice, sorghum, wheat, beans, and pulses), oilseeds (rapeseed, canola, flax seed and olive seeds), fruits, vegetables and beverages (fruit juices, tea, coffee, cocoa, beer and wine) are the main sources of dietary polyphenols. Fruits like apple, grape, pear, cherry and various berries contain up to 200-300mg polyphenols/ 100 g fresh weight. A glass of red wine or a cup of coffee or tea contains about 100mg polyphenols. Their total dietary intake may be about 1g/ day, which is about 10x higher than of vitamin C and 100x higher than those of vitamin E and carotenoids. The major constituents of tea polyphenols of tea polyphenols constitute up to 30 per cent of the dry weight of green leaves and 9-10% of dry weight of black tea leaves. Citrus fruits are main sources of flavomones, and hesperidin is found in abundance (120-250mg/l) in orange juice. Fruits, particulary onions are rich source of quercetin. Anthocyanins are pigments of fruits such as cherries, plums, strawberries and red currant, ranging from 0.15 to 4.5 mg/g in fresh berries. Soyabean is main source of isoflavonoids like genistein and daidzein that have important role in prevention of cancer and osteoporosis. People who consume traditional diets rich in soy and tea rarely have breast, uterus and prostate cancer.
Bitter ways to slow aging: Cumin or jeera, extensively used in Indian cuisine, is known to possess antiparasitic and antimicrobial properties. It is also used to cure fewer and as a painkiller. One of the variants of cumin, bitter cumin (kalijiri), has been studied for its antianagsic and astringent properties. It is dried seed of the herb Centatherum anthelminticum and used to treat a wide range of diseases from vitiligo to hyperglycemia. Now, a research suggests that bitter cumin contains high levels of antioxidants. ROSs, also known as free radicals, are produced as part of the metabolic processes necessary for life. These are required or various functions like cell growth and energy production. But conversely their increased concentrations and non-removal from of the body can lead to abnormalities like neurodegerative disorders and cancer. Anti oxidants detoxify these free radicals and help in their removal from the body. By neutralising these ROS, antioxidants also slow down the aging process. Common antioxidantsinclude vitamin C and E.
Research conducted at CFTRI (Central Food Technological Research Institute), Mysore, on bitter cumin treated with a combination of CH3COCH3 (actone), CH3OH ( methanol) and H2O (water). the antioxidant activity of bitter cumin extracts were then characterised using various free radical scavenging tools like DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS ( 2,2′-azino-bis-3-ethyl benzthiazoline-6-sulphonic acid). To validate the results, extracts were also tested for their reducing power –ability to donate electrons. Higher the reducing power of the sample better is the antioxidant activity. The results revealed that bitter cumin extracts were strong antioxidants with different magnitude of potency in scavenging different ROS at the µg concentration. The phenol extract of bitter cumin contains an array of phenolic compounds which may be responsible for its antioxidant activity. The extracts were also strong electron donors and hence potential reducing agents. Bitter cumin extracts were also able to minimize oxidative damage to DNA, one of the most detrimental effects of free radicals. It was also found that radical scavenging activity of bitter cumin phenols is the highest among all plant phenols. Previous studies have reported number, type and concentrations of phenols in plants exhibit extreme diversity. IT has been observed on broad spectrum analysis, reported phenolic compounds, antioxidant, anto-hyperglycemic, antimicrobial activity of bitter cumin. It is a native to the Upper Egypt but now grown in countries across the world especially India, North Africa, China and the US.
Although there are several enzyme systems within the body that scavenge free radicals, the principle micronutrient (vitamin) antioxidants are vitamin E, β-carotene, and vitamin C. Additionally, Se (selenium), a trace metal that is required for proper function of one of the body’s antioxidant enzyme systems, is sometimes included in this category. The body cannot manufacture these micronutrients so they must be supplied in the diet. Antioxidants destroy free radicals”… In recent years, a new term ‘neutraceuticals’ has been coined, which combines ‘nutrition’ and ‘pharmaceutical’ to mean that they have health-enhancing role or physiologically active food components that can have certain prophylactic and / or healing properties and can be used as preventive drugs or as food supplements, Stephen de Felice, Director of NYFIM (New York’s Foundation for Innovation in Medicine) is credited with the first use of the term neutraceutical. These compounds include disease preventing phytochemicals or phytonutrients present in food stuffs; for example, isoflavones in soyabean, lycopene in tomatoes, lignans in flaxseed, and sulphoraphane in broccoli, which have protective effect against cancer. In future, phytochemicals of neutraceutical importance may be used as preventive medicine.