ANTIOXIDANTS

Tapeshwar Yadav(Lecturer)

BMLT, DNHE, M.Sc. Medical Biochemistry

ANTIOXIDANTSDEFINITION : An antioxidant is a

molecule capable of inhibiting the oxidation of other molecules.

Oxidation reactions can form free radicals and these start chain reactions that damage cells .

Antioxidants terminate these chain reactions by removing free radical intermediates and inhibit other oxidation reactions

TYPES OF ANTIOXIDANTSThese are three types I) Enzymatic and Non enzymatic

antioxidants: They are present in both Extracellular and

Intracellular Environment. Enzymatic Antioxidants -S.No

Antioxidant Location Function

A Glutathione peroxidase

Mitochondria & Cytosol

Removal of H2O2 and Organic Hydro peroxide

B Catalase Mitochondria & Cytosol

Removal of H2O2

Non Enzymatic AntioxidantsS. No

Antioxidant

Location Function

A Carotenoids

Lipid soluble antioxidants in membrane tissue

Removal of ROS

B Bilirubin Product of heme metabolism in blood

Extracellular antioxidants

C Glutathione

Non-protein thiol in cell

Cellular oxidant defense

D α- Lipoic acid

Endogenous thiol

Serves as substitute for Glutathione, recycling vit-C

E Viamin C Aqueous phase of cell

Free scavenger, recycle vit- E

F Vitamin E Cell Chain breaking Antioxidant

G Uric acid Product of Purine Metabolism

Scavenging of OH radical

II) Natural and Dietary Sources a) Natural sources : Chlorophyll derivatives , Carotenoids ,

Essential oils , Phytosterols, Alkaloids, Phenolics, Nitrogen containing compounds.

b)Dietary antioxidants : Camosol ,Rosmanol , Camosoic acid, III) Based on Defense Mechanism : a) Preventive Antioxidants : Peroxidase, Catalase , Lactoferrin,

Carotenoids Etc….

b)Radical scavenging Antioxidants : Vitamin C and Carotenoids. c) Repair and DENOVO antioxidants d) Enzyme inhibitor Antioxidants

Functions of Antioxidants :Antioxidants such as vit- C & vit- E boost

our immune system.Certain phytochemicals have beneficial

effect on heart diseases.Antioxidants lower the level of LDL-

cholesterol, thus preventing plaque deposition in the blood vessels.

It is beneficial in cancer prevention.Antioxidants neutralize substances that can

damage the genetic material by oxidation.

Vitamins as Antioxidants CAROTENES :A carotene is one of four Antioxidants that are

vital for our general health and wellbeing. There are four carotene compounds : α-Carotene, β-Carotene, γ-Carotene, δ-Carotene.α-Carotene & β-Carotene are the powerful

antioxidantsβ-Carotene is an antiageing micronutrient and

play a significant role in reducing the effects of certain illnesses such as heart disease, decreased immune function, cataracts, cancer.

Much like beta, alpha-carotene is found in foods like: Carrots ,Sweet potatoes ,Squash ,Brussel

sprouts,Kiwi, Spinach, Broccoli, Kale, Mang0, Cantaloupe

ASCORBIC ACID(VIT-C) : It is a hydrophilic antioxidant.Neutralization of H2O2Maintain healthy collagen in skin, Repair damaged tissue, healthy teeth and bones, boost immune systemAs a free radical fighter helps ward off wrinkles and

many illnesses linked to oxidation, cataracts, arthritis, heart disease and cancer

Vitamin C functions as an anti-inflammatory, and helps the body fight inflammatory diseases, including fibromyalgia, and chronic fatigue, angina, bronchitis, bruises, canker sores, constipation, diabetes, vitamin C helps the body absorb iron, it is also useful in treating iron deficiency and anemia.

Sources : Broccoli, Strawberries, Kale, Citrus fruits like oranges, limes, and lemons, Tomatoes ,Bell peppers Cabbage, Watermelon, potatoes and spinach.

TOCOPHEROLS ( vit- E) : It is a lipid soluble and among them α-

tocopherol is biologically active It is an antioxidant present in all cellular

membranes and protects against lipid peroxidation and normal ageing process.

It directly acts on oxyradicals and serve important chain breaking antioxidant.

Vitamin E is used as treatment for many chronic diseases including Alzeimer’s disease, osteoarthritis and prostate enlargement.

Sources : Peanut oil, cotton seed oil, sunflower oil, whole grains, green leafy vegetables.

ΑLPHA LIPOIC ACID : It is universal anti oxidant It is also called Thioctic acid It helps to converts glucose to energy, detoxifies

the body, fights inflammation in the skin and helps stabilizes blood sugar

It plays a key role in recycling other important antioxidants such as ascorbic acid, α tocopherol and Glutathione.

It penetrates through tissues composed of fat and those made of water such as Nervous tissue and Heart

Sources : Spinach , Liver , Brewer’s yeast

Minerals as Antioxidants SELENIUM : It is an essential trace element and is proved to be

antioxidant It works with Vit –E in fighting free radicals It is required for the functioning of an important enzyme

Glutathione peroxidaseSelenium protects the body from free radical damage in

two ways a) It is incorporated into proteins to make

selenoproteins (acts as antioxidant) b) It helps in the body manufacture its own natural

antioxidant Glutathione It reduce colorectal, lung and prostrate cancerSources : sea foods, meats ,organ meats, whole grains.

Hormones as AntioxidantsMELATONIN : It is a powerful antioxidant that can easily

cross cell membranes and the Blood brain barrier

It does not undergo redox cyclingMelatonin cannot be reduced its former

state as it forms stable compounds after reacting with free radicals

It has been referred as a terminal /Suicidal antioxidant

Metabolic AntioxidantGLUTATHIONE : It is the mother of all Antioxidants It is a Tripeptide made of Cysteine, Glutamic

acid and Glycine It is a Hydrophillic antioxidant found in

every cell in Human body It is the most important antioxidant due to

the fact that it is directly found in cells and breakdown the free radicals with in the cells, hence it is often called “Mother of all Antioxidants”.

Sources: Garlic, Broccoli, Onions, Dairy products, Oats, Chicken, Watermelon.

URIC ACID : It is the most abundant and uncomplicated

antioxidant found in the body It has the highest concentration of any oxidant found

in blood cells and is hydrophilic and it accounts for more than half of all antioxidant capacity

It is a marker of oxidative stress and is a powerful scavenger of singlet oxygen and hydroxyl radicals.

Elevated levels of uric acid in diseases associated with oxidative stress such as stroke & atherosclerosis, Parkinson’s disease.

Sources: sweetbreads, liver, beef, meat extracts etc..

Ceruloplasmin : Inhibits Iron and copper dependent lipid

peroxidation. Transferrin : Binds to iron and prevents iron catalysed free radical

formation. Albumin : Can scavenge free radicals formed on its surface Bilirubin : Protects the albumin bound free fatty acid from

peroxidation Haptoglobulin : Binds to free haemoglobin and prevents acceleration

of lipid peroxidation.

Essential oils as Antioxidants These are a class of volatile oils obtained by

steam distillation and these may be extracted from plants, fruits, flowers, barks, roots and seeds.

Advantages: Due to their small molecular size, they can easily

penetrate the skin tissue. As essential oils are lipid soluble they are

capable of penetrating the membranes easily even in conditions when oxygen deficiency is present.

They serve as powerful antioxidants & they prevent mutants and oxidants in cells.

Pro-oxidants These are chemicals that induce oxidative

stress either through creating reactive oxygen species or inhibiting antioxidant systems

The oxidative stress produced by these chemicals can damage cells and tissues

Some substances can acts as either antioxidants or prooxidants depending on the specific set of condition.

Eg: Transitional metals (Mn, Fe, Cu), Vit C and Uric acid.

Uses in technology Food preservatives:Antioxidants used as food additives to help

guard against food deteriorationExposure to oxygen & sunlight are the 2 main

factors in the oxidation of food.Natural preservatives- vit C & vit ESynthetic antioxidants- Propyl gallate, Tertiary

butyl hydro quinone(TBHQ), Butylated hydroxy anisole(BHA), Butylated hydroxy toluene(BHT)

Unsaturated fats- drying, smoking, salting or fermenting.

Industrial uses:Antioxidants are frequently added to

industrial products.Common use : stabilizers in fuels &

lubricants to prevent oxidation In gasolines to prevent polymerization that

leads to the formation of engine –fouling residues.

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