Free redical vs antioxident

FREE REDICAL AND ANTIOXIDANTS

WHAT ARE FREE RADICAL? Free radicals are very unstable and react quickly

with other compounds, trying to capture the needed electron to gain stability.

TYPES OF FREE RADICAL

1. Superoxide, O2-

2. Hydrogen peroxide, H2O2

3. Hydroxyl radical, OH-

4. Singlet oxygen, 1O2

5. Hydroperoxy radical, HOO-

6. Lipid peroxide radical, ROO-

7. Nitric oxide, NO-

8. peroxynitrite, ONOO-

PROPERTIES OF FREE RADICAL1. Highly reactive2. Very short half-life3. Generate new radicals by chain reaction4. Cause damage to biomolecules, cells and tissues

Most free radicals in biological systems are derivatives of oxygen (Reactive Oxygen Species, ROS), but there are also derivatives of nitrogen (Reactive Nitrogen Species, RNS), Reactive Metabolites or Intermediates.

REACTIVE OXYGEN SPECIES (ROS) Superoxide (O2

.-) Hydrogen Peroxide (H2O2) Hydroxyl Radical (OH.) Singlet oxygen, 1O2

Reactive Oxygen Species is used in a broad sense to collectively free radicals (O2

.-, OH.) and non-free radicals (H2O2, 1O2, which are extremely reactive) of the biological system.

GENERATION OF FREE RADICAL1. Cellular metabolism:- About 1- 4% of oxygen taken up in the body is converted to free radicals. They are constantly produced during the normal oxidation of foodstuffs.a) Due to leaks in the electron transport chain in

mitochondria. b) Some enzymes such as xanthine oxidase and aldehyde

oxidase form superoxide anion radical or hydrogen peroxide.

c) Macrophage also produces NO from arginine by the enzyme nitric oxide synthase. This is also an important anti-bacterial mechanism.

SOURCES OF OXYGEN FREE RADICALIn mitochondria:

- generation of energy - ATP- glucose, fatty acids, amino acids- O2 2H2O

4e-+4H+

- leakage of O2-. (superoxide)

H2O2 (hydrogen peroxide)

2. Environmental effects:-A. Due to drug metabolismB. Due to damages caused by UV or X-raysC. Cigarette or alcohol

Excessive smokingAlcohol

High fat foods

FREE RADICAL FORMATION

Industrial pollution Pesticides & herbicides

Environmental pollution

HARMFUL EFFECTS OF FREE RADICAL

A. Free Radical and biomolecules1. Proteins:- Cause oxidation of sulfhydryl groups, and modification of

AA. ROS may damage protein by fragmentation, aggregation results in the loss of biological activity of proteins.

2. Lipids:- The polyunsaturated lipid molecules of cell membranes

are particularly susceptible to damaging free radicals process and contribute to the uncontrolled chain reaction (lipid peroxidation).

3. Carbohydrates:- Glycation increases the susceptibility of proteins to

the attack by free radicals.4. Nucleic acid:- Cause DNA strand breaks, fragmentation of bases

and deoxyribose results in cytotoxicity and mutations.

B. Diseases1. Cardiovascular diseases (CHD):- ox-LDL, formed by the action

of free radicals, promote CHD and atherosclerosis (AS). 2. Cancers:- damage DNA and cause mutation and cytotoxicity,

play a key role in carcinogenesis.3. Inflammatory diseases:- damage on the extracellular

components such as collagen and hyaluronic acid, promote glomerulonephritis and ulcerative colitis.

4. Respiratory diseases:- destroy endothelium and cause lung edema. Cigarette smoke contains free radicals and promotes the production of more free radicals.

5. Diabetes mellitus:- Destruction of islets results in pathogenesis.

6. Male infertility:- reduce sperm motility and viability.7. Aging process8. Others:- such as Parkinson's disease, Alzheimer’s

disease, multiple sclerosis, liver cirrhosis, muscular dystrophy.

ANTIOXIDANTS The substance present in low concentrations

relative to the oxidizable substrate that significantly delays or reduces oxidation of the substrate.

They reduce the effect of dangerous oxidants by binding together with these harmful molecules, decreasing their destructive power.

They can also help repair damage already sustained by cells.

They may be considered as the scavengers of free radicals.

During this reaction the antioxidant sacrifices itself by becoming oxidized.

However, antioxidant supply is not unlimited as one antioxidant molecule can only react with a single free radical. Therefore, there is a constant need to replenish antioxidant resources.