Natural Food Antioxidants
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Due to increasing awareness about various effects of antioxidants, it has become an essential part to understand and thoroughly study the various antioxidants and their biological effect on day to day lifestyle. Oxidative stress being major problem these days leading to chronic diseases. The lean towards natural products is tremendously increased due to the revolution around us. Hence, “non chemical” or plant-derived aspect of living is accepted. In this chapter, basics of study starts with definition of antioxidants, knowledge of free radical, combating mechanism of antioxidants, generation of oxidative stress due to disproportion of free radical and antioxidants have been explained. Various antioxidants along with their sources are also included. Importance of antioxidants in living, a wellbeing state is studied which may prove to be useful in the future as well. Research and development in this particular field has led its roots deep down. Most attention is paid towards oral administration, such as fruits, vegetables, etc., in order to achieve the desired benefits. Therefore, it is vital to include food rich in antioxidant in our diet.
KeywordsAntioxidants Free radicals Oxidative stress Carotenoids Flavonoids etc.
Due to the increasing awareness about the foodstuff consumption, the culinary skills have more bent towards the health promoting aspect of life. Today’s world demand for chemical free products, even in food and other aspects as cosmetics, pharmaceuticals, etc. Hence, wave of natural products is emerging the new trends. Natural products have a rich history in terms of nontoxic, non-harming but potent effect. Contemporary research on antioxidants has been significantly seen in food. Customer has become more interested by “NON-CHEMICAL” antioxidants in food . Antioxidant is defined as, “Any substance that, when present at low concentrations compared to those of an oxidisable substrate, significantly delays or prevents oxidation of that substrate” . Antioxidants obtained from herbs and spices such as turmeric , parsley piert , bushes which used as additives in jellies ; day to day used common vegetables such as potatoes , white cabbage , dried tomatoes , ginger ; and fruits such as grapes , blueberries, and strawberries . There are many other sorts of things rich in antioxidants. It is observed that in processing such as drying, freeze drying of fruits and vegetables, the antioxidant property will be affected. Hence, maximum optimization is practiced in industries like dietary fiber [12, 13]. Main mechanism of antioxidants is to balance the free radical that causes oxidation of protein, carbohydrates, lipid, and nucleic acid. Mechanism malfunctioning causes many dangerous diseases like cancer, atherosclerosis, diabetes, etc. which are worst age-prone diseases . Generation of free radical is due to the uncoupled flow of electrons or unpaired valence electron in an atom, molecule, or ion. Considering oxygen as a main reactive element, many subspecies such as reactive oxygen species (ROS), include superoxide (O2−), peroxyl (ROO), hydroxyl (HO), nitric oxide (NO), alkoxyl (RO), etc. are most dreadful free radicals which affects the cell directly . Similarly, nitrogen-centered free radicals also exist. Further, these free radicals become nonreactive free radical such as hydrogen peroxide, peroxy nitrate, etc. though free radicals played significant role in biological evolution, but still works as scavengers today. The toxic effect of these radicals is highly remarkable .
2 Free Radicals and Oxidative Stress
Natural defensive mechanism by human body 
Removal by enzymes with processes like excision, resynthesis, and rejoining of DNA strands.
Removal by enzymes like methionine reductase and cellular proteases.
Chain breaking antioxidants like tocopherols, etc.
3 Oxidative Stress
Damage occurring in DNA:- Accumulation of ROS can affect DNA in numerous ways, such as degradation of bases; ss or ds DNA breakage; purine, pyrimidine, or sugar-bound modifications; mutations, deletions, or translocations; and cross-linking with proteins. This change leads to carcinogens, aging, cardiovascular diseases, etc. For example, at transcription factor binding site, there is development of 8-OH-G DNA which changes the expression of the particular genes.
Damage occurring in proteins:- ROS can lead to shattering of peptide chain, modification of electrical charge of proteins, cross-linking of proteins, and oxidation of specific amino acids and consequently leads to amplified exposure to proteolysis by degradation by specific proteases. More prone to oxidation are cysteine and methionine residues in proteins. Metal catalyzed oxidation is more prone in enzymes with metals close to active sites which showed alteration in activities.
Damage occurring in lipids:- Interruption in lipid bilayer membrane by ROS which induces lipid peroxidation outcomes in inactivation of membrane-bound receptors, enzymes, and rise tissue permeability. Inactivating cellular protein by forming cross linkage is ability of MDA and unsaturated aldehydes. 4-Hydroxy-2-nonenal has proven to activate epidermal growth factor receptor [EGFR] and induces fibronectin production. Isoprostanes and thiobarbituric acid are some of the products of lipid peroxidation, which act as an indirect biomarker of oxidative stress .
Moreover, the part of antioxidants is very essential in order to combat free radical and oxidative stress. Several kinds of antioxidants are existing within body. There are various enzymatic and nonenzymatic antioxidants. Former are endogenous antioxidants, which are produced by body while later exist as food supplement to the body. Example include enzymatic- Superoxide Dismutase (SOD), Catalase (CAT), etc. and nonenzymatic-Vitamins, flavonoids, etc. . Enzymatic antioxidants contribute to first-line defense whereas the nonenzymatic antioxidant contributes to second-line defense .
4.1 Vitamin C (Fig. 2)
CLASS: - Vitamins
CHEMICAL NAME: −2-oxo-L-threo-hexono-1,4-lactone2,3-enedio
STRUCTURAL CHEMISTRY:- The chief dietary forms of vitamin C are L-ascorbic and dehydroascorbic acid. Stability of ascorbic acid is impacted by pH. It is highly stable between pH 4 and 6. Affected by degree of heating, surface area exposed to water, oxygen, pH, and presence of transition metals. Exist in L and D forms .
MODE OF ACTION:- Chain termination reaction or by reaction with other radicals 
APPLICATION:- Prevents scurvy, vasodilation in bronchial and coronary arteries, etc. 
SOURCES: - Broccoli, white cabbage, cauliflower .
4.2 Vitamin E (Fig. 3)
CHEMICAL NAME:- 2-methyl-2-(4′,8′,12′-trimethyltridecyl)-chroman-6-ol(parent compound) 
STRUCTURAL CHEMISTRY:- Exist in four forms α, β, γ, δ in which α- tocopherol is mostly effective as antioxidants . Chromone group is responsible for the antioxidant activity of molecule, while the kinetics of transport and retention within membranes is regulated by the phytyl group largely .
MODE OF ACTION:- Peroxyl radical scavenger 
APPLICATION:- Inhibits the oxidation of low-density lipoprotein cholesterol .
SOURCES: - Soybean, Oats, Corns, Evening primrose oils, etc. 
4.3 Lycopene (Fig. 4)
CHEMICAL NAME:- Ψ,Ψ-Carotene 
STRUCTURAL CHEMISTRY:- It is an aliphatic hydrocarbon with 13 double bond in the structure. It doesn’t have vitamin A activity as expressed by other carotenoid. It is the longest carotenoids due to eleven conjugated carbon-carbon double bond .
MODE OF ACTION:- –Singlet oxygen quenching, peroxyl radical scavenging 
SOURCES:-Watermelon, tomatoes, etc. 
4.4 β- Carotene (Fig. 5)
CHEMICAL NAME:- β, β-carotene 
STRUCTURAL CHEMISTRY:- Contributes to form vitamin A in body 
MODE OF ACTION:- Singlet oxygen quenching 
APPLICATION:- Reduces risk in lung cancer 
SOURCES:-Mango, etc. 
4.5 Gallic Acid (Fig. 6)
CLASS:- Polyphenols 
CHEMICAL NAME: - 3, 4, 5-trihydroxybenzoic acid 
STRUCTURAL CHEMISTRY:- It is a planar molecule, with four stable conformers. The presence of hydroxyl group and any other functional group determines the antioxidant activity .
MODE OF ACTION: - Acting as an electron donor or hydrogen atom donor 
SOURCES:-Longan seed, mango kernel 
4.6 Catechin (Fig. 7)
CHEMICAL NAME:- 2-(3,4-dihydroxyphenyl)-3,4-dihydro-2Hchromene-3,5,7-triol 
STRUCTURAL CHEMISTRY:- Position and number of hydroxyl group in the moiety determines antioxidant activity. Presence of catechol moiety and unsaturation increases activity in catechins. (+) catechin is more effective .
MODE OF ACTION:- Inhibits lipid peroxidation 
APPLICATION:- Anti-allergic, Anti-inflammatory, Antiviral, Anti-proliferative, and Anti-carcinogenic activities 
SOURCES:- Apples, hops, tea, beer, etc. 
4.7 Resveratrol (Fig. 8)
CLASS:- Stilbenes 
CHEMICAL NAME:- 3, 4′, 5 trihydroxystilbene 
MODE OF ACTION:- Increases plasma antioxidant activity and decreases lipid peroxidation 
APPLICATION:- Anti-inflammatory, Neuroprotective, and Antiviral properties 
SOURCES: - Peanuts, Mulberries, Grapes 
4.8 Glutathione (Fig. 9)
CLASS:- Thiols 
CHEMICAL NAME:- (GSH)γ-glutamylcysteinylglycine 
MODE OF ACTION:- Glutathione peroxidase mechanism 
SOURCES:- Mushroom etc. 
4.9 Coumarin (Fig. 10)
CHEMICAL NAME:- 1,2-benzopyrone 
STRUCTURAL CHEMISTRY:- They show chemical similarities with flavonoids and classified depending on the benzene and lactone ring present. Promising antioxidant activity is due to the benzopyrone ring .
MODE OF ACTION:- Free radical scavenger 
SOURCES:- Bilberry, cloudberry, green tea, etc. .
CLASS:- Minerals 
MODE OF ACTION:- Combines with several enzymes and protein and show variable activity .
APPLICATION:- Useful in heart diseases, cancer 
SOURCES:- Fish, egg, meat, legumes, etc. 
5 Antioxidants in Human Health
Has oxidative impairment been involved within the disease pathophysiology? (Amplified lipid peroxidation or oxidation of protein or DNA should be associated with the disease).
Is the oxidative activity act as an essential pathophysiological feature of the disease? (As sometimes it is the offshoot generated by common tissue damage and cell loss, hence, if not the major cause, the resulting impairment may cause avoidable morbidity).
Are there known defects in antioxidant status?
Where is the place at which oxidative damage occurs? (May be intracellular, extracellular or in membranes or else lipoproteins)
Will the antioxidant reach that area? (The amount of antioxidants should be sufficient to reach protected areas such as CSF, etc.)
Will the chosen antioxidant hit the target? (For example, preventive antioxidants are more potent in iron-dependent lipid peroxidation but fails for iron-independent reactions.)
Can the antioxidant be given and tolerated in the necessary doses?
Is antioxidant therapy “safe”? .
After understanding question one can predict the use of antioxidants in diseases. Many such are reported such as use of tomato extract in hypertension. Hypertension is most widely spread diseases which affect billions of people over the globe. Types are grade I–II. Any one medication merely controls the patients’ blood pressure (BP), weather the disease is considered mild to moderate. Hence, two or more drugs along with the alteration of lifestyle are done. The termination is associated with adverse effects in patients. Hence, focus over natural products provokes much faster these days. Antioxidant vitamin has shown to improve vascular function, as a result, daily supply may reduce the threat of BP values. Tomato (Lycopersicon esculentum Mill.) is a source of vitamins and carotenoids. Tomato juice (rich in lycopene) also showed greater than before resistance against low-density lipoprotein (LDL) to oxidation in type 2 diabetic individual . Natural antioxidants are suitable drug for the deteriorating bugs such as Alzheimer’s disease (AD) and Parkinson’s disease (PD) as there are complex targets as well as pathways associated and pathogenesis is complex. Natural antioxidants had protecting effects on neuron in neurodegenerative diseases. Oxidative stress causes nerve cell death which leads to stroke, trauma, and diseases such as AD and PD. Flavonoids, polyphenols and nicotine were effect natural antioxidants against these diseases. As per reports, Ginkgo-Biloba extract (EGb) provide defense against hypoxic damage and inhibit ROS formation in cerebellar neurons. The flavonoid such as ginkgolides and biolobalids were useful. The powerful action against several diseases such as atherosclerosis, the diseases associated with postmenopausal estrogen deficiency, the cancer associated with breast and prostate which depends on hormones is shown by the soy isoflavones. It was reported that genistein showed protection against neurons . The major causes of deaths are due to cancer. Around 13% of mortality is due to cancer and if continue will reach in the year 2030 to 1.1 crores. It becomes a very vital consideration reducing cancer affected patients. Studies showed that the sufficient consumption of fruits and vegetables, specifically carotenoid-rich diet decreased the risk of more than a few types of cancers. Antioxidants like α-carotene, lutein, lycopene, β-cryptoxanthin, β-carotene, and α-Tocopherol has shown an inverse relationship to lung cancer. The oral, pharynx, and larynx cancer were prevented by the use of β-carotene. More than half of the oral and throat cancers were reduced by ingestion of natural substances. A study also showed that 40–50% risk of cancer was lowered due to high intake of fruits and vegetables. Colon cancer risk was reduced due to the consumption of vegan diet (Active plus high sources of natural antioxidants) . Oxidative stress plays a major part in both Type 1 as well as Type 2 diabetes pathogenesis. Oxidation of LDL has increased the risk of atherosclerosis with people with diabetes. Higher markers of oxidation and lipid peroxides are more common in diabetic patients. Oxidation stress leads to more breakage of DNA strands and oxidized pyrimidines in Type 1 patients as compared with normal subjects. Elevation of blood glucose level is observed in altered purines. A major source of free radicals is linked with diabetic complication, i.e., is glycation finish products. As a result, many alterations are seen, such as the release of superoxide, reduction in the glutathione levels . After cancer, cardiovascular diseases (CVDs) are prominent reason of death. Flavonoids prove to be boon in CVDs as a reduction in the mortality rate was observed in Western country such as Europe and the United States. Oxidation makes the etiology of CVDs difficult. Endothelial cell injuries and deleterious vasodilator effects are primarily caused by oxidative stress. Antioxidant polyphenol lead to improvement in endothelial functions, hence, play a very important role. In vitro studies show that flavonoids extracted from Euterpeoleracea pulp showed atheroprotective effect. Various other diseases such as obesity, aging, inflammatory bowel diseases, cataract , renal disorders, infertility, pregnancy, etc.  also showed promising results when natural antioxidants came into the picture.
Change in the standard of living, food habits, pollution, and stress, we are further intended towards ROS-induced oxidative stress even though the presence of endogenous antioxidants mechanism. Diseases more than 100 are reported not less due to ROS. This leads us to explore more about the antioxidants present naturally. Proper understanding the development of antioxidants leads to enormous research and treatment in various disorders associated. Food which is prime asset of bioactive compounds and antioxidants should be added to our body nourishment which is the best advice provoking to the better life. Ongoing research and development about antioxidants may pave a path in therapeutic analysis of antioxidants for better treatment of tomorrow. Role of antioxidants in human health can become additional apparent .
The various aspects of antioxidants with examples are explained in the above discussion. There is increasing proof that consumption of a variety of antioxidant present in natural foods might lower the danger of significant health illnesses owing to their antioxidant activity, among different mechanisms. Variation in the mechanism gives every antioxidant a unique way to combat the oxidative stress and manage free radicals within body. The main cause of oxidative stress in the body and various diseases are discussed as well. The classification of antioxidants gives us a brief idea about the structural summary and proper information on the individual. Due to the increasing need of natural products and “NON–CHEMICAL” approach, industries are more optimized in the process as well as consumption from daily food intake. Natural antioxidants have a huge way to pave and more development will lead to a healthy life and save lives.
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