Division of Biochemistry Division of Biochemistry Rajah Muthiah Medical CollegeRajah Muthiah Medical College

Annamalai UniversityAnnamalai University

Molecules that protect tissues from any free radical (molecule with unpaired electron).

Organic molecule that Minimize or prevent cellular damage

Numerous vitamins, minerals phytochemicals and certain enzymes

What are free What are free radicals?radicals?

Atom or group of atoms with an odd (unpaired) number of electron

Capable of independent existence, but are highly reactive

Initiates a chain reaction (dominoe effect)Leads to disruption of a living cellOverload of free radicals has been linked

to diseases including heart disease, liver disease and certain cancers

Formation of free Formation of free radicalradical

Metabolism of oxygen by cells form by products – free radicals

When the body breaks down certain medications

Through pollutantsOxygen molecule is a free radical

Free radical species of Free radical species of pathological importancepathological importance

Super oxide ion O2-

Hydroxyl OH-Nitric oxide NO-Ferryl ion FeO2+

Perferyl ion FeO22+

Allyl RAlkoxyl RO.Peroxyl ROO.“R” is a polymer of – CH2- -CH=group

Role of transition metal in Role of transition metal in free radical formationfree radical formation

Fenton’s ReactionFe2+ + H2O2 Fe3+ + OH + OH-

Presence of catalytic iron or copper increases the rate of formation of free radicals

Iron is carefully sequestered by a variety of proteins

Iron sequestrationIron sequestrationTransferrin and haemopexin (during

transport)

Transferrin receptors (during uptake)

Ferritin and haemosidrin (during storage)

Role of free radicals in Role of free radicals in respiratory burstrespiratory burst

Free radicals are generated by neutrophils,monocytes, eosinophils

Used to kill internalized bacteria after phagocytosis

This metabolic event is known as respiratory burst

Activation of neutrophil NADPH – dependent oxidase

Formation of superoxide O2 - hydrogen peroxide ( formed from

superoxide by SOD) Fe3+ (catalyst)

MPO (myloperoxidase)

Formation of hydroxyl Radical (OH) HOcl (hypochlorous acid)

Destruction of internalized bacteria

Chronic granulomatous disease – NADPH oxidase system is defective

Repeated severe infections

Harmful effects of free Harmful effects of free radicalsradicals• Free radicals are very unstable and highly reactive

• Forms schiff’s bases and cause damage to DNA• Lipid peroxidation - Peroxyl radicals

• In presence of Iron / copper ions

• Cytotoxic aldehydes (malondialdehydes and hydroxy noneal)

• Chemicaly modify proteins and DNA

• May produce mutations or cancer

Antioxidants – Protection Antioxidants – Protection against against

free radical damagefree radical damageAntioxidants confer protection by safely

interacting with free radicalsMode of actionChelating the transitional metal catalystsChain breaking reactionsReducing the concentration of reactive

radicalsScavenging initiating radicals

AntioxidantsAntioxidantsSuperoxide dismutaseCatalaseEnzymes Glutathione peroxidase

Natural – Vitamin E, Vitamin C, Selenium Carotenes

Non-enzymesBHTSynthetic BHA

Enzymes (Cytoprotective Enzymes (Cytoprotective enzymes)enzymes)

1. Superoxide dismutase : Zn/cu containign enzyme – cytosol Manganese – metalloprotein – mitochondria

O2- + O2

- + 2H+ H2O2 + O2

SOD

2. Catalase Peroxisome and cytosol of the cell

2H2O2 H2O + O2

catalase

3. Glutathione peroxidase Selenium containing mettaloenzyme

H2O2 + 2GSH GSSG + 2H2O Glutathione peroxidase

G.6.PD deficiency – Inability to form NADPH

causes hamolysis – hamolytic anaemia

Non-EnzymesNon-EnzymesTocopherols Functions as a chain breaking

antioxidantsAnti cancer effectFood source – Asparagus, corn oil,

hazel nuts, raw almonds, Soya beans

RDA – Man 10 mg (15 IU) Women 8 mg (12 IU)

Vit. CAnti cancer effectCombined action with tocopherolsBeneficial in smokersFood source : Amla, guava, line, lemon,

green leafy vegetablesRDA – 60 – 70 mg /dayAdditional requirement 20-40% more in

pregnancy in lactation

CarotenesScavengers of free radicals (alkoxyl and peroxyl)Beta carotenes – lowers LDL cholesterol levelsFodo soruce : Apricots, carrots, broccoli, mangoes,

peaches, peppers, pump kinsAstaxanthin – Fat soluble carotenoid – Fights

cancer and AMDRDA – Man 1000 retional equivalent (5000 IU) Women 800 retional equivalent (4000 IU)1 retional equivalent = 6 g of beta carotene

Glutathione Inactivates hydrogen peroxide and lipid peroxidesFood source: Asparagus, Avacado

SeleniumMineral forms a part of the enzyme glutathione

peroxidase that disposes free radicalsFood source : brazil nuts, sea food, organ meat

SpirulinaMicroscopic, single cell blue – green algaeFood source: Available in form of pills, flakes (sprinkle over

salad) powder

Zinc (Zn)Important component of enzymesFood source: Eggs, meat, sea food, tofu

Flavanoid Anti inflammatory plant antioxidant protects against heart

disease and cancerFood source: Blue berries, carrots, egg plants, orangesProtects ascorbic acid from being destroyed

LuteinFound in eye’s retina, carotenoids slows progression of

AMDFood source : broccoli, corn, egg yolk

PhytoestrogenIso flavones or natural plant estrogen Food source: Green tea, grapes

N-Acetylcysteine (NAC)Increases elvel fo glutathione Food source: Eggs, granola, meats

Coenzyme Q10 : Also known as ubiquinone

Lipid present in almost every plant and animal

Prevents LDL cholesterol oxidationFood Source: Broccoli, spinach, peanuts

Alpha lipoic acid : ALAPrevents oxidation of LDL, protein and DNAFood source: Beef, potato, spinach

Assessment of free Assessment of free radical damage and radical damage and antioxidant statusantioxidant status

Protein oxidationDetected by fluorescence spectroscopyLipid peroxidationDiene conjucates : early marker of lipid

peroxidation 235 – 255 mmThiobarbituric acidAbsorbance measured at 532 nm or 553

nm

Estimation of Anti-oxidant Estimation of Anti-oxidant statusstatus

Assessment of cytoprotective enzymes

a) Superoxide dismutaseb) Catalasec) Glutathione peroxidase

Diets rich in Diets rich in AntioxidantsAntioxidants

• Soya beans Green leafy vegetables• Carrots Almonds• Mangoes Amla• Pumpkin Lemon• Sea food Blue berries• Oranges Green tea• Grapes Peanuts• Sunflower oil Corn oil

Wish youWish youless oxidative stress

More antioxidantsLonger life Thank You