What is free radicals There are many different types of free radicals, for example: Where do free radicals come from? What is Antioxidant ? TYPES OF ANTIOXIDANTS Natural Sources of Antioxidants Mode Of Action
Free Radicals Vs Anti-Oxidants 
 Evaluating Anti-oxidant Activity

1. Antioxidants
By Aya Mohammed and Youssor Ridha
MSc students at Alnahrain University

2. What is free radicals
atoms with an unpaired number of electrons formed when oxygen
interacts with certain molecules, once formed these highly reactive
radicals can start a chain reaction

3. There are many different types of free
radicals, for example:
• superoxide anion (O2-)
• hydroxyl radical (OH )
• hydrogen peroxide (H2O2)
• singlet oxygen (1O2 )

4. Where do free radicals come from?
• normal metabolism
• Environmental pollutants ( radiation, herbicides, pesticides )
• smoking

6. What is Antioxidant ?
• A molecule that inhibit the oxidation of other molecules
• i.e. remove free radicals

7. TYPES OF ANTIOXIDANTS
Based on chemical nature
• Enzymatic : peroxidase , Catalase
• Non enzymatic : Vitamin E, Vitamin C, Uric acid, α- Lipoic acid
Based on Defense Mechanism
• Preventive Antioxidants : Peroxidase, Catalase
• Radical scavenging Antioxidants : Vitamin C and Carotenoids.

8. Natural
Sources of
Antioxidants
Terpenes
tetraterpenoid
carotenoids
Lycopene
Terpenes
tetraterpenoid
carotenoids
B-carotene
(Vitamin A)
polyphenols
flavonoids
Rubin
Ascorbic acid
(vitamin C)
Flavonoids
Catechin +
Epicatechin
Tomato Carrot Cocoa Beans
Orange,
Strawberry,
Pepper, Broccoli

9. Mode Of Action
Free Radicals Vs Anti-Oxidants
Free radicals damage cell membrane
• Initiation :lipid peroxidation process
by stealing electron from cholesterol
that attached to phosphate head of
phospholipid in cell membrane lead
to change head properties and initiate
destabilization of the Membrane
• Chain reaction of free radicals : chain
propagation
• Termination : Erosion of membrane
Anti-oxidants prevent phospholipids
peroxidation + avoid cell membrane
damage
• Scavenging initiating radicals
• Chain breaking reaction : prevent chain
propagation
• Able to repair oxidizing radicals directly
1- Cell Membrane

11. Free Radicals
• Steal electron from the sugar part of
nucleotide (oh) in 3 end of each
nucleotide
• Break in DNA chain causing
mutation aging and cancer
2- DNA
Anti-oxidants
• Reducing the free radicals
• Scavenge free radicals
Mode Of Action
Free Radicals Vs Anti-Oxidants

14. Free radical
production
𝑜2
−
, 𝐻2
𝑂2
OH
Tissue damage
Antioxidants
Scavenging initiating radicals
( enzymatic anti-oxidants)
Chelating transition metals
( non enzymatic anti-oxidants)
Repair mechanism
(prevent chain propagation)
Transition
metals
F𝑒2+
,
C𝑢2+

15. Evaluating Anti-oxidant Activity
Assay Principle
DPPH
Antioxidant reaction with an organic
radical
ORAC
Antioxidant reaction with peroxyl
radicals

16. DPPH Assay
free radical in nature
with purple color
DPPH + Anti-oxidant DPPHH
Hydrogen donor Reduced form with
yellow color
rapid, simple and inexpensive in comparison to other methods
With a UV spectrometer
DPPH shows a strong absorptionmaximum at 517 nm (purple)
Therefore, the antioxidant effect can be easilyevaluated by the decrease of UV absorptionfrom 517 nm ( yellow
color).
Anti-oxidant activity=
OD (control ) – OD ( sample )
OD (control )
x 100

17. ORAC Assay “Antioxidant Power”
Peroxyl O𝐻+, + Fluorescein fluorescence
Peroxyl O𝐻+, + Fluorescein + Anti-oxidant fluorescence
By preventing the
oxidation of
fluorescein
oxidation of fluorescein
Free radical Probe

18. At the end we use antioxidant in :
• Anti-aging cream
• Sunblock
• Supplement
Drug candidate
• Tirilazad is an antioxidant steroid derivative that inhibits the lipid
peroxidation that is believed to play a key role in neuronal death in
stroke. It demonstrated activity in animal models of stroke, but human
trials demonstrated no effect

19. Thank You