A Review on Dietary Antioxidants
Dr. Suja C,, Shuhaib.B, Muhammed Abdurahman, Hunaida khathoom , Simi k
Crescent College of Pharmaceutical Sciences, Madayipara, Payangadi R.S.(Post), Kannur,
Kerala.
Abstract:
An antioxidant is a molecule stable enough to donate an electron to a rampaging free radical and
neutralize it, thus reducing its capacity to damage. Mechanism of action of anti oxidant are a
chain- breaking mechanism by which the primary antioxidant donates an electron to the free
radical present in the systems and removal of ROS/reactive nitrogen species initiators by
quenching chain-initiating catalyst. The article present a broad review on the dietary sources,
several disease prevention by dietary anti oxidant .In this review study the cancer prevention,
aspect of plant poly phenol as dietary anti oxidant in human health and the cardio protective
effect, anti diabetic effect, anti aging effect , neuro protective effect are studied. From this review
study we have come to the conclusion that dietary antioxidants are good for prevention of many
of the lifestyle diseases, cancer etc as prevention is better than cure.
Key word: Anti oxidant, Mechanism, Poly phenol etc
Introduction:
Free radicals
A free radical can be defined as any molecular species capable of independent existence that
contains an unpaired electron in an atomic orbital. The presence of an unpaired electron results in
certain common properties that are shared by most radicals. Many radicals are unstable and
highly reactive1. They can either donate an electron to or accept an electron from other
molecules, therefore behaving as oxidants or reductants. Free radicals are derived either from
normal essential metabolic processes in the human body or from external sources such as
exposure to X-rays, ozone, cigarette smoking, air pollutants, and industrial chemicals. Free
radical formation occurs continuously in the cells as a consequence of both enzymatic and
nonenzymatic reactions. Enzymatic reactions, which serve as source of free radicals, include
those involved in the respiratory chain, in phagocytosis, in prostaglandin synthesis, and in the
cytochrome P-450 system. Free radicals can also be formed in nonenzymatic reactions of oxygen
with organic compounds as well as those initiated by ionizing reactions.
An antioxidant is a molecule stable enough to donate an electron to a rampaging free radical and
neutralize it, thus reducing its capacity to damage. These antioxidants delay or inhibit cellular
damage mainly through their free radical scavenging property. These low-molecular-weight
antioxidants can safely interact with free radicals and terminate the chain reaction before vital
molecules are damaged. Some of such antioxidants, including glutathione, ubiquinol, and uric
acid, are produced during normal metabolism in the body2. Antioxidants act as radical scavenger,
hydrogen donor, electron donor, peroxide decomposer, singlet oxygen quencher, enzyme
inhibitor, synergist, and metal-chelating agents.
Mechanism of action of antioxidants
Two principle mechanisms of action have been proposed for antioxidants. The first is a chainbreaking mechanism by which the primary antioxidant donates an electron to the free radical
present in the systems. The second mechanism involves removal of ROS/reactive nitrogen
species initiators (secondary antioxidants) by quenching chain-initiating catalyst. Antioxidants
may exert their effect on biological systems by different mechanisms including electron
donation, metal ion chelation, co- antioxidants , or gene expression regulation3.
Levels of antioxidant action
The antioxidants acting in the defence systems act at different levels such as preventive, radical
scavenging, repair, and the fourth line of defence, i.e., the adaptation.The first line of defence is
the preventive antioxidants, which suppress the formation of free radicals. Although the precise
mechanism and site of radical formation in vivo are not well elucidated yet, the metal-induced
decompositions of hydro peroxides and hydrogen peroxide must be one of the important source.
The second line of defence is the antioxidants that scavenge the active radicals to suppress chain
initiation and/or break the chain propagation reactions. Various endogenous radical-scavenging
antioxidants are known: some are hydrophilic and others are lipophilic. Vitamin C, uric acid,
bilirubin, albumin, and thiols are hydrophilic, radical-scavenging antioxidants, while vitamin E
and ubiquinol are lipophilic radical-scavenging antioxidants. Vitamin E is accepted as the most
potent radical-scavenging lipophilic antioxidant4.The third line of defense is the repair
antioxidants. The proteolytic enzymes, proteinases, proteases, and peptidases, present in the
cytosol and in the mitochondria of mammalian cells, recognize, degrade, and remove oxidatively
modified proteins and prevent the accumulation of oxidized proteins.5
Types of antioxidants
Enzymatic
Cells are protected against oxidative stress by an interacting network of antioxidant enzymes.
Here, the superoxide released by processes such as oxidative phosphorylation is first converted
to hydrogen peroxide and then further reduced to give water. This detoxification pathway is the
result of multiple enzymes, with superoxide dismutase’s catalyzing the first step and then
catalases and various peroxidases removing hydrogen peroxide. Superoxide dismutase
Superoxide dismutases (SODs) are a class of closely related enzymes that catalyze the
breakdown of the superoxide anion into oxygen and hydrogen peroxide.SOD enzymes are
present in almost all aerobic cells and in extracellular fluids6.
In humans three forms of superoxide dismutase are present. SOD1 is located in the cytoplasm,
SOD2 in the mitochondria, and SOD3 is extracellular. The first is a dimer (consists of two units),
while the others are tetramers (four subunits). SOD1 and SOD3 contain copper and zinc, while
SOD2 has manganese in its reactive center7.Catalase is a common enzyme found in nearly all
living organisms, which are exposed to oxygen, where it functions to catalyze the decomposition
of hydrogen peroxide to water and oxygen. Hydrogen peroxide is a harmful by-product of many
normal metabolic processes: to prevent damage, it must be quickly converted into other, less
dangerous substances8. Glutathione systems include glutathione, glutathione reductase,
glutathione peroxidases, and glutathione S-transferases. This system is found in animals, plants,
and microorganisms. Glutathione peroxidase is an enzyme containing four selenium-cofactors
that catalyze the breakdown of hydrogen peroxide and organic hydroperoxides
Nonenzymatic
Ascorbic acid------ or “vitamin C” is a monosaccharide anti oxidant found in both animals and
plants. As it cannot be synthesized in humans and must be obtained from the diet, it is a vitamin.
Most other animals are able to produce this compound in their bodies and do not require it in
their diets. In cells, it is maintained in its reduced form by reaction with glutathione, which can
be catalyzed by protein disulfide isomerase and glutaredoxins.
Glutathione ------ is a cysteine-containing peptide found in most forms of aerobic life. It is not
required in the diet and is instead synthesized in cells from its constituent amino acids.
Glutathione has antioxidant properties since the thiol group in its cysteine moiety is a reducing
agent and can be reversibly oxidized and reduced.
Melatonin------also known chemically as N-acetyl-5-methoxytryptamine,is a naturally occurring
hormone found in animals and in some other living organisms, including algae. Melatonin is a
powerful antioxidant that can easily cross cell membranes and the blood–brain barrier. Unlike
other antioxidants, melatonin does not undergo redox cycling, which is the ability of a molecule
to undergo repeated reduction and oxidation 9
Tocopherols and tocotrienols------Vitamin E is the collective name for a set of eight related
tocopherols and tocotrienols, which are fat-soluble vitamins with antioxidant properties. Of
these, α-tocopherol has been most studied as it has the highest bioavailability, with the body
preferentially absorbing and metabolizing this form. It has been claimed that the α-tocopherol
form is the most important lipid-soluble antioxidant, and that it protects membranes from
oxidation by reacting with lipid radicals produced in the lipid peroxidation chain reaction.
Uric acid------ accounts for roughly half the antioxidant ability of plasma. In fact, uric acid may
have substituted for ascorbate in human evolution. However, like ascorbate, uric acid can also
mediate the production of active oxygen species
Literature review
Diet as a source of antioxidants
Synthetic and natural food antioxidants are used routinely in foods and medicine especially those
containing oils and fats to protect the food against oxidation. There are a number of synthetic
phenolic antioxidants, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA)
being prominent examples. In view of increasing risk factors of human to various deadly
diseases, there has been a global trend toward the use of natural substance present in medicinal
plants and dietary plats as therapeutic antioxidants. It has been reported that there is an inverse
relationship between the dietary intake of antioxidant-rich food and medicinal plants and
incidence of human diseases. The use of natural antioxidants in food, cosmetic, and therapeutic
industry would be promising alternative for synthetic antioxidants in respect of low cost, highly
compatible with dietary intake and no harmful effects inside the human body. Many antioxidant
compounds, naturally occurring in plant sources have been identified as free radical or active
oxygen scavengers. Attempts have been made to study the antioxidant potential of a wide variety
of vegetables like potato, spinach, tomatoes, and legumes.
The commonly used dietary antioxidant includes (with common/ayurvedic names in brackets)
Allium cepa (Onion), A. sativum (Garlic, Lahasuna),Amomum subulatum (Greater cardamom,
Bari elachi), Andrographis paniculata (Kiryat), Azadirachta indica (Neem, Nimba), Bacopa
monniera (Brahmi), Camellia sinensis (Green tea), Cinnamomum verum (Cinnamon),Curcma
longa (Turmeric, Haridra), Emblica officinalis (Inhian gooseberry, Amlaki),Mangifera indica
(Mango, Amra), Momordica charantia (Bitter gourd), Murraya koenigii (Curry leaf), Picrorrhiza
kurroa (Katuka), Piper beetle and Zingiber officinalis (Ginger)10.
Cancer chemoprevention through dietary antioxidants
It was estimated that nearly one third of all cancer details in United States could be prevented
through appropriate dietary modification. Various dietary antioxidants have shown considerable
promise as effective agents for cancer prevention by reducing oxidative stress which has been
implicated in the development of many diseases, including cancer. Therefore, for reducing the
incidence of cancer, modifications in dietary habits, especially by increasing consumption of
fruits and vegetables rich in antioxidants are increasingly advocated. This review presents an
extensive analysis of the key findings from studies on the effects of dietary antioxidants such as,
curcumin, lupeol, and pomegranate,against cancers of skin ,prostate,breast and liver .Cancer is a
disease in which a series of cumulative and genetic changes that are initiated in a normal cell
occur .Chemoprevention is a strategy to completely halt or slow the process of cancer
development by intervening in the process of carcinogenesis.11
Curcumin
Curcumin is a major yellow pigment in turmeric that impartsa yellow colour to food and is
widely used as a spice. It is derived from the roots of plant Curcuma longa. In MCF-7 breast
cancer cells, telomerase activity decreased with increasing concentrations of curcumin, may be
due to downregulation of hTERT expression. Curcumin caused a steady decrease in the level of
human telomerase reverse Transcriptase (hTERT) mRNA in MCF-7 cells12.Curcumin inhibited
camptothecin, mechlorethamine, and using a in vivo model of human breast cancer, dietary
supplementation with curcumin was found to significantly inhibit cyclophosphamide-induced
tumor regression which was accompanied by a decrease in activation of apoptosis by
cyclophosphamide and decreased JNK (JUN N TERMINAL KINASE) activation.13
Pomegranate
The pomegranate (Punica granatum L.) fruit has been used for centuries in ancient cultures for
its medicinal purposes. Pomegranate fruits are widely consumed in fresh and beverage forms as
juice. Ellagic acid, caffeic acid, luteolin, and punicic acid, all important components of the
aqueous compartments or oily compartment of pomegranate fruit were reported to inhibit invitro
invasion of human PC-3 prostate cancer cells in an assay employing matrigel artificial
membranes. It was shown that PFE treatment of human prostate cancer PC-3 cells resulted in a
dose dependent inhibition of cell growth/cell viability and induction of apoptosis14.
Lupeol
Lup-20-en-3-ol (Lupeol), a triterpene found in fruits such as such as olive, mango, strawberry,
grapes, and figs, in many vegetables, and in several medicinal plants, is used in the treatment of
various diseases. It possesses strong anti-inflammatory, antiarthritic, antimutagenic, and
antimalarial activity in vitro and in vivo systems. Lupeol has been shown to act as a potent
inhibitor of protein kinases and serine proteases and to inhibit the activity of DNA topoisomerase
II, a target for anticancer chemo therapy. It has also been reported to improve the epidermal
tissue reconstitution and induces differentiation and inhibits the cell growth of melanoma
cells.15Lupeol treatment resulted in significant inhibition of cell viability in a dose-dependent
manner and caused apoptotic death of prostate cancer cells. Lupeol was found to induce the
cleavage of PARP protein and degradation of acinus protein with a significant increase in the
expression of FADD protein and Fas receptor.16
Plant polyphenols as dietary antioxidants in human health and disease
Polyphenols are secondary metabolites of plants and are generally involved in defense against
ultraviolet radiation or aggression by pathogens. In the last decade, there has been much interest
in the potential health benefits of dietary plant polyphenols as antioxidant. Epidemiological
studies and associated meta-analyses strongly suggest that long term consumption of diets rich in
plant polyphenols offer protection against development of cancers, cardiovascular diseases,
diabetes, and osteoporosis and neurodegenerative diseases
Polyphenols are naturally occurring compounds found largely in the fruits,
vegetables, cereals and beverages. Fruits like grapes, apple, pear, cherries and berries contains up
to 200–300 mg polyphenols per 100 grams fresh weight. The products manufactured from these
fruits, also contain polyphenols in significant amounts.1 7 Typically a glass of red wine or a cup
of tea or coffee contains about 100 mg polyphenols. Cereals, dry legumes and chocolate also
contribute to the polyphenolic intake.Polyphenols are secondary metabolites of plants and are
generally involved in defense against ultraviolet radiation or aggression by pathogens. In food,
polyphenols may contribute to the bitterness, astringency, color, flavor, odor and oxidative
stability. Polyphenols and other food phenolics is the subject of increasing scientific interest
because of their possible beneficial effects on human health. This review focuses on the present
understanding of the biological effects of dietary polyphenols and their importance in human
health and disease.
Structure and classes of polyphenols
1. Phenolic acids: Phenolic acids are found abundantly in foods and divided into two
classes:derivatives of benzoic acid and derivatives of cinnamic acid. The
hydroxybenzoic acid content of edible plants is generally low, with the exception of
certain red fruits, black radish and onions, which can have concentrations of several
tens of milligrams per kilogram fresh weight. The hydroxycinnamic acids are more
common than hydroxybenzoic acids and consists chiefly of p-coumaric, caffeic, ferulic
and sinapic acids.18
2. Flavonoid : Flavonoids comprise the most studied group of polyphenols. This group
has a common basic structure consisting of two aromatic rings bound together by three
carbon atoms that form an oxygenated heterocycle . More than 4,000 varieties of
flavonoids have been identified, many of which are responsible for the attractive
colours of the flowers, fruits and leaves.Based on the variation in the type of
heterocycle involved, flavonoids may be divided into six subclasses: flavonols,
flavones, flavanones,flavanols,anthocyaninsand isoflavones . Individual differences
within each group arise from the variation in number and arrangement of the hydroxyl
groups and their extent of alkylation and/or glycosylation. Quercetin, myricetin,
catechins etc. are some most common flavonoids. 19
3. Stilbenes: Stilbenes contain two phenyl moieties connected by a two-carbon
methylene bridge. Occurrence of stilbenes in the human diet is quite low. Most
stilbenes in plants act as antifungal phytoalexins, compounds that are synthesized only
in response to infection or injury. One of the best studied, naturally occurring
polyphenol stilbene is resveratrol (3,4',5 trihydroxystilbene), found largely in grapes.
A product of grapes, red wine also contains significant amount of resveratrol.20
Stilbenes
4.
Lignans: Lignans are diphenolic compounds that contain a 2,3-dibenzylbutane
structure that is formed by the dimerization of two cinnamic acid residues . Several
lignans, such as secoisolariciresinol, are considered to be phytoestrogens. The richest
dietary source is linseed, which contains secoisolariciresinol (up to 3.7 g/kg dry
weight) and low quantities of matairesinol.21
Poly phenols and human diseases
Epidemiological studies have repeatedly shown an inverse association between the risk of
chronic human diseases and the consumption of polyphenolic rich diet. The phenolic groups in
polyphenols can accept an electron to form relatively stable phenoxyl radicals, thereby disrupting
chain oxidation reactions in cellular components. It is well established that polyphenol-rich foods
and beverages may increase plasma antioxidant capacity.22This increase in the antioxidative
capacity of plasma following the consumption of polyphenol-rich food may be explained either
by the presence of reducing polyphenols and their metabolites in plasma, by their effects upon
concentrations of other reducing agents (sparing effects of polyphenols on other endogenous
antioxidants), or by their effect on the absorption of pro-oxidative food components, such as
iron. Consumption of antioxidants has been associated with reduced levels of oxidative damage
to lymphocytic DNA. Similar observations have been made with plyphenol-rich food and
beverages indicating the protective effects of polyphenol.
Cardioprotectve effect
Number of studies has demonstrated that consumption of polyphenols limits the incidence of
coronary heart diseases. Atherosclerosis is a chronic inflammatory disease that develops in
lesion-prone regions of medium-sized arteries. Atherosclerotic lesions may be present and
clinically silent for decades beforebecoming active and producing pathological conditions such
as acute myocardial infarction, unstable angina or sudden cardiac death.
Polyphenols are potent inhibitors of this type of oxidation is considered to be a key
mechanism in development of atherosclerosis. Other mechanisms by which polyphenols may be
protective against cardiovascular diseases are antioxidant, anti-platelet, anti-inflammatory effects
as well as increasing HDL, and improving endothelial function. Polyphenols may also contribute
to stabilization of the atheroma Plaque.Quercetin, the abundant polyphenol in onion has been
shown to be inversely associated with mortality from coronary heart disease by inhibiting the
expression of metalloproteinase1 (MMP1), and the disruption of atherosclerotic plaques.
Polyphenols may also exert antithrombotic effects by means of inhibiting platelet aggregation.
Consumption of red wine or non-alcoholic wine reduces bleeding time and platelet aggregation.
Thrombosis induced by stenosis of coronary artery is inhibited when red wine or grape juice is
administrated.Polyphenols can improve endothelial dysfunction associated with different risk
factors for atherosclerosis before the formation of plaque; its use as a prognostic tool for
coronary heart diseases has also been proposed.
Anti diabetic effect
Impairment in glucose metabolism leads to physiological imbalance with the onset of the
hyperglycemia and subsequently diabetes mellitus. There are two main categories of diabetes;
type-1 and type-2. Studies have shown that several physiological parameters of the body get
altered in the diabetic conditions.
Long term effects of diabetes include progressive development of specific complements such as
retinopathy, which affects eyes and lead to blindness; nephropathy in which the renal functions
are altered or disturbed and neuropathy which is associated with the risks of amputations, foot
ulcers and features of autonomic disturbance including sexual dysfunctions. Numerous studies
report the antidiabetic effects of polyphenols. Tea catechins have been investigated for their antidiabetic potential. Polyphenols may affect glycemia through different mechanisms, including
the inhibition of glucose absorption in the gut or of its uptake by peripheral tissues. The
inhibition of intestinal glycosidases and glucose transporter by polyphenols has been studied.
Individual polyphenols, such as (+)catechin, (-)epicatechin, (-)epigallocatechin, epicatechin
gallate, isoflavones from soyabeans, tannic acid, glycyrrhizin from liquorice root, chlorogenic
acid and saponins also decrease S-Glut-1 mediated intestinal transport of glucose. Saponins
additionally delay the transfer of glucose from stomach to the small intestine.22
Anti-aging effect
Aging is the accumulation process of diverse detrimental changes in the cells and tissues with
advancing age, resulting in an increase in the risks of disease and death. Among many theories
purposed for the explaining the mechanism of aging, free radical/oxidative stress theory is one of
the most accepted one.
Several researches suggest that the combination of antioxidant/anti-
inflammatory polyphenolic compounds found in fruits and vegetables may show efficacy as antiaging compounds. Subset of the flavonoids known as anthocyanins, are particularly abundant in
brightly colored fruits such as berry fruits and concord grapes and grape seeds.
Anthocyanins are responsible for the colors in fruits, and they have been shown to have potent
antioxidant/anti-inflammatory activities, as well as to inhibit lipid peroxidation and the
inflammatory mediator’s cyclo-oxygenase (COX)1.
Fruit and vegetable extracts that have high levels of flavonoids also display high total antioxidant
activity such as spinach, strawberries and blueberries. It is reported that the dietary
supplementations (for 8 weeks) with spinach, strawberry or blueberry extracts in a control diet
were also effective in reversing age-related deficits in brain and behavioral function in aged
rats.A recent study demonstrates that the tea catechins carry strong anti-aging activity and
consuming green-tea rich in these catechins, may delay the onset of aging.23
Neuro protective effect
Oxidative stress and damage to brain macromolecules is an important process in
neurodegenerative diseases. polyphenols are highly antioxidative in nature, their consumption
may provide protection in neurological diseases.It was observed that the people drinking three to
four glasses of wine per day had 80% decreased incidence of dementia and Alzheimer’s disease
compared to those who drank less or did not drink at all.Resveratrol, abundantly present in wine
scavenges O2 and OH in vitro, as well as lipid hydroperoxyl free radicals, this efficient
antioxidant activity is probably involved in the beneficial effect of the moderate consume of red
wine against dementia in the elderly.
It was found that the consumption of fruit and vegetable juices containing high concentrations of
polyphenols, at least three times per week, may play an important role in delaying the onset of
Alzheimer’s disease. Polyphenols from fruits and vegetables seem to be invaluable potential
agents in neuroprotection by virtue of their ability to influence and modulate several cellular
processes such as signaling, proliferation, apoptosis, redox balance and differentiation of
Dopaminergic neurons in the substantia nigra zona compacta.
Effect of dietary antioxidants on cardiovascular disease
Antioxidant Intakes and CVD
Intake of fruits and vegetables has long been associated with a lower risk for several chronic
diseases mediated by oxidative stress, including CVD. Dietary Antioxidan t such as Vit
E,Carotenoids, and polyphenols were thought to responsible for the cardiovascular protective
effect through suppressing oxidative stress suggested by preclinical studies and epidemiological
studies.
Dietary Vitamin E
The effects of dietary vitamin E intake on CVD risk have been investigated by several large
cohort studies. An inverse association between dietary total vitamin E intake and heart disease
risk was reported by several studies though; findings were controversial when a vitamin E
supplement was used. The Nurses’ Health Study (NHS) conducted in 1980 involved more than
87,000 U.S. female nurses between 34 and 59 years old with no history of CVD to investigate
the association between dietary vitamin E intake and CVD risk. After an 8-year follow-up,
women in the top quartile of total vitamin E intake had a 34% lower risk (RR: 0.66; 95% CI:
0.50, 0.87) of coronary disease compared with those in the bottom quintile. Further analysis from
the study showed that the inverse association was only attributable to vitamin E supplement
intake rather than vitamin E from diet.antioxidants such as vitamin E, carotenoids, and
polyphenols were thought to responsible for the cardiovascular protective effect through
suppressing oxidative stress suggested by preclinical studies and epidemiological studies
Dietary Vitamin C
Although studies on plasma vitamin C were limited, dietary vitamin C intake has been widely
studied in relation to CVD risk in several prospective cohort studies. Three out of eleven studies
identified found significant protective association between dietary vitamin C intake and CVD
outcomes. The most significant result was observed in the NHS, in which 85,118 nurses were
followed for 16 years since 1980. Women in the top quartile of total vitamin C intake had a 27%
lower risk (RR: 0.73; 95% CI: 0.57, 0.94) of nonfatal MI and fatal CHD compared with those in
the bottom quintile. Further analysis from the study showed that the inverse association was only
attributable to vitamin C supplement intake rather than vitamin C from diet.
Dietary Carotenoids
Among the cohort studies of dietary carotenoids, seven out of ten studies reported significant
associations between dietary carotenoids and CVD outcomes in a protective direction, especially
for dietary β-carotene intake. In the NHS cohort, 73,286 women had been followed up for 12
years since 1984. A study reported inverse associations between intakes of α-carotene, βcarotene and CAD, and no associations between intakes of lutein/zeaxanthin, lycopene, or βcryptoxanthin and CAD. In the HPFS (Health Professional Follow up Study) , smoking status
was a significant effect modifier in the association between carotene intake nutrients.
Antioxidant Vitamin Supplements
Previously reviewed large cohort studies have suggested that antioxidant vitamins, especially
vitamin E, vitamin C, and β-carotene may reduce CVD risk. Accordingly, these vitamin
supplements were widely tested in several large-scale, randomized controlled trials to investigate
their protective Polyphenols are widely distributed in the human diet, mainly derived from plant
foods such as fruits, vegetables, nuts, seeds, tea, red wine, and cocoa. Polyphenols are
characterized by having at least one aromatic ring with one or more hydroxyl groups attached
and have been reported to have more than 8000 structures.24
Dietary TAC (total antioxidant capacity)
Given the evidence that single antioxidant supplements showed no beneficial effects on
preventing CVD, as well as the fact that diet high in antioxidants such as fruits, vegetables, and
tea has been widely reported to have beneficial health effects, dietary TAC that considers all the
antioxidants present in diet and the synergistic effects between them thus are drawing increasing
attention. Dietary TAC has been found to be positively associated with several diet quality scores
as well as typical individual antioxidants, indicating dietary TAC represents dietary quality and
antioxidant status in these study populations.
Conclusion
An antioxidant is a molecule stable enough to donate an electron to a free radical and neutralise
it, thus reducing its capacity to damage. These antioxidants delay or inhibit cellular damage
mainly through the free radical scavenging property.
Nowadays human beings are being affected by numerous diseases. Providing diets enriched with
antioxidants is a critical tool against these diseases. Antioxidants are also an effective agent for
cancer prevention as it reduces the oxidative stress which has been implicated in the
development of cancer.
Polyphenols are secondary metabolites of plants and are generally involved in defence against
UV radiation or aggression by pathogen. In the last decade, there has been much interest in the
potential health benefits of dietary plants polyphenols as antioxidants. Studies have demonstrated
that consumption of polyphenols limits the incidence of coronary heart diseases.
From this review study we have come to the conclusion that dietary antioxidants are good for
prevention of many of the lifestyle diseases, cancer etc as prevention is better than cure.
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