Beginner Guide to Free Radicals, Oxidative Stress and Natural Antioxidants
CONTENTS (Free Radicals and Oxidative Stress):
Free Radicals
Types of free radicals
Sources of free radicals
Reactive Oxygen Species (ROS)
Reactions by which Free Radicals are produced
Role of Free Radicals in biological systems
Oxidative Stress
Molecular Effect of Oxidative Stress
Measurement of Oxidative Stress
Protection against ROS Damage
Diseases caused by Free Radicals
CONTENTS (Natural Antioxidants):
Antioxidants
Natural Antioxidants
Mechanism of Action
Classification of natural antioxidants
Biological Activities of natural antioxidants
References
Hubble Asteroid Hunter III. Physical properties of newly found asteroids
Free Radicals, Oxidative Stress and Natural Antioxidants by Maliha Rashid.pptx
1. Free Radicals, Oxidative Stress and Natural
Antioxidants
by
Maliha Rashid
M.Phil BIOT
PMAS Arid Agriculture University Rawalpindi, Pakistan
1
2. Table of Contents
1. Free Radicals
2. Types of free radicals
3. Sources of free radicals
4. Reactive Oxygen Species (ROS)
5. Reactions by which Free Radicals are
produced
6. Role of Free Radicals in biological
systems
7. Oxidative Stress
8. Molecular Effect of Oxidative Stress
9. Measurement of Oxidative Stress
10. Protection against ROS Damage
11. Diseases caused by Free Radicals
2
3. Free Radicals
• molecules having unpaired electrons
• Reactive as they have the tendency to complete their octet
• Unstable –try to become stable by accepting or donating electrons
• Very reactive- very harmful (can damage the surrounding cells) causes
cell injury
• Short life span
3
6. Sources of Free Radicals
Endogenous Sources
Environmental
Sources
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7. Endogenous Sources
• Electron Transport Chain
• Nitrite Oxide Synthase
• NADPH Oxidase Reaction/Respiratory Burst
• Xanthine Oxidase Reaction
• Lipoxygenase Pathway (Conversion of arachadonic acid via the lipoxygenase pathway is
associated with an increase of ROS)
• Lipid Peroxidation
7
8. Respiratory Burst
• Respiratory burst(also called oxidative burst) is the rapid release of reactive
oxygen species ( superoxide anion and hydrogen peroxide) from different types of
cells.
• Usually it denotes the release of these chemicals from immune cells, such as
neutrophils and macrophages because they are infected by different bacteria or
fungi.
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10. Xanthine Oxidase Reaction
• Xanthine oxidase is the enzyme required to produce uric acid by the
breakdown of purine nucleotides.
• The uric acid itself, as well as the reactive oxygen species released
during the enzymatic reaction, can have detrimental effects on the
body.
• Gout is a common condition that occurs due to elevated uric acid
production via this mechanism.
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12. Lipid Peroxidation
• Lipid peroxidation is an oxidative chain reaction in which one lipid
molecule after another becomes oxidized to the maximum possible
extent or so as to form a lipid peroxide (i.e., a lipid molecule
containing one or more O–O bonds)
12
15. Reactive Oxygen Species
• Most important free radicals in the body
• Derived from Oxygen
Examples
1. Superoxide anion (O2
.−)
2. Hydrogen Peroxide (H2O2)
3. Hydroxyl Peroxyl radical (HOO-)
4. Hydroxyl Radical (OH.)
5. Singlet Oxygen (O2)
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17. Physiological Activities of Free Radicals
• When maintained at low or moderate concentrations, free radicals play several
beneficial roles for the organism.
1. synthesize some cellular structures
2. cellular signaling pathway
3. induction of a mitogenic response
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18. Oxidative Stress
• A disturbance in the balance between reactive species/free radicals and
antioxidants
• Under normal conditions, cells are able to balance the production of
oxidants and antioxidants
• Oxidative stress occurs when there is imbalance in the cells due to an
increase in the production of free radicals or a decrease in
antioxidants.
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27. Natural Antioxidants
• Primarily extracts of herbs and plant materials
• Has electron donating and chain breaking properties
• have potential to balance the irregulated oxidative stress
• Protect body against diseases
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28. Mechanism of Action
• Inhibit oxidative stress by neutralizing free radicals
• Donate electron to the free radical
• Terminates chain reaction
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29. Classification of Natural Antioxidants
1. Vitamins
2. carotenoids
3. polyphenols
4. small antioxidant molecules
5. enzymes
6. trace elements
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30. Sources of Natural Antioxidants Explanation
Vitamins Vitamin A, C,E
Carotenoids B-carotene
Polyphenols phenolic acids, coumarins, flavonoids, stilbenes and
lignans
Small antioxidant molecules Enzymes, Ubiquinone, sulfur containing compounds
Trace Elements Selenium
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32. Role in various diseases
Natural Antioxidants Role in diseases
Vitamin E protects against cataracts and restore multidrug
resistance in tumour cells
Polyphenols vasorelaxant and antihypertensive properties
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33. References
1. Butnariu and Samfira, J Bioequiv Availab (2012)
2. Pickrell AM, Fukui H, Moraes CT (2009) The role of cytochrome c oxidase deficiency in ROS
and amyloid plaque formation. J Bioenerg Biomembr 41: 453-456.
3. Rizzo AM, Berselli P, Zava S, Montorfano G, Negroni M, et al. (2010) Endogenous antioxidants
and radical scavengers. Adv Exp Med Biol 698: 52- 67.
4. Gustafsson AB, Gottlieb RA (2008) Heart mitochondria: gates of life and death. Cardiovasc Res
77: 334-343.
5. Akinci M, Kosova F, Cetin B, Sepici A, Altan N, et al. (2008) Oxidant/antioxidant balance in
patients with thyroid cancer. Acta Cir Bras 23: 551-554..doi.org/10.4172/jbb.10000e13
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Editor's Notes
1. Phagocytes keeps free radicals and release on the entry of pathogens.. Chronic granulomatous disease.. Defective NADPH pathway.due to which the certain types of bacteria cannot be killed in the body …role in fibroblast, endothelial cells, cardiac myocytes’..Nitric oxide is an important free radical in signaling pathway. Cell-to-cell messgenger required for a proper blood flow modulation..
including atherosclerosis, ischemia, hypertension, cardiomyopathy, cardiac hypertrophy, and congestive heart failure
