This document discusses antioxidants and free radicals. It begins by introducing oxidation and how it contributes to diseases, then defines free radicals as unstable molecules that can damage other molecules. It explains how free radicals cause damage through oxidation and discusses oxidative stress. The document lists sources of free radicals both internal from metabolism and external from environmental factors. It defines reactive oxygen species as examples of free radicals containing oxygen. The document discusses how antioxidants work by donating electrons to neutralize free radicals. It lists the different levels of antioxidant action and types of antioxidants including enzymes, vitamins, and phytochemicals.

1. Antioxidant
By
omer faris
saif jabbar

2. Introduction
– Oxidation: chemical reaction that involves
transfer of electrons from one compound to
other. Contributes to diseases such as
cancer, heart disease. Oxidation causes
loss of flavour and colour in foods. To
prevent oxidation antioxidants are used.

3. Free radical :
Free radicals are atoms, ions, or molecules that contain an
unpaired electron. The unpaired electron makes them
unstable and highly reactive.free radical generally , highly
reactive molecule that can react with any molecule and
cause damage .

4. How can free radical cause
damage to other molecule?
– In a process called oxidation, free radicals steal
electrons from other molecules—fats, proteins, cell
membranes, and even DNA—altering the fundamental
structure of the affected molecule. One unbalanced
molecule may not sound like a major concern, but
oxidation sets off a chain reaction by damaging a cell’s
DNA, structure, and ability to function. Over time,
oxidative damage accumulates and contributes to
aging and a variety of degenerative diseases.

5. What is oxidative stress ?
– Oxidative stress is the oxidative damage that results from an
imbalance between free radicals and your body’s store of
antioxidants.
– Oxidative stress can cause :
1. Aging
2. Several degenerative conditions such as arthritis, heart
disease, hypertension, Alzheimer’s disease, Parkinson’s
disease, muscular dystrophy, and more.

6. Effect of FR on human
– Excessive ROS can induce oxidative damage in cell constituents and promote
a number of degenerative disease and aging .
– ROS have been implicated in more than 100 disease:
1. Breast cancer
2. CVD-atherosclerosis
3. Eye disorder
4. Diabetic complication

7. Free Radical Theory Of Aging
(FRTA)
– This theory states :
– organisms age because of accumulated free radical
damage to cells and DNA. The theory states that
accumulative damage to cell components and
connective tissue leads to wrinkles, decreased
physical capability, increased susceptibility to
disease, and death .

8. Lipid
peroxidation

9. Where Do Free Radicals Come
From?
– There are many types of free radicals, but when we discuss them in a health capacity, we’re
referring to those that contain oxygen in the molecule, known collectively as reactive oxygen
species (ROS).
– There are many sources of free radicals:
1. As a natural by product of cellular metabolism.
Oxygen is an essential element of life , and every cell in your body requires it for cellular metabolism. During
cellular metabolism, cells use oxygen to convert food into a form of energy the body can use, called ATP .Free radicals
are a natural by product of cellular metabolism.
2. Free radicals are generated by inflammation(phagocytic cell ,neutrophils and macrophage ),
stress, illness, and aging.
3. Hazardous environmental sources such as pollution, toxic metals, alcohol, cigarette smoke,
radiation, industrial chemicals, and medications expose us to free radicals.

10. Externally generated sources of
free radical :

11. Example of free radical : ROS
– Reactive oxygen species (ROS) are chemically reactive chemical species
containing oxygen. Example include peroxide, superoxide, hydroxyl radical,
and singlet oxygen.
– In a biological context, ROS are formed as a natural by product of the normal
metabolism of oxygen and have important roles in cell
signaling and homeostasis. However, during times of environmental stress
(e.g., UV or heat exposure), ROS levels can increase dramatically. This may result
in significant damage to cell structures. Cumulatively, this is known as oxidative
stress. ROS are also generated by exogenous sources such as ionizing radiation, as
well as endogenous sources.

12. ROS

13. Antioxidant
Antioxidants are man-made or natural substances that
may prevent or delay some types of cell damage.
Antioxidants are found in many foods, including fruits and
vegetables. They are also available as an enzyme within
the body and as dietry supplement .

14. How does antioxidant work ?
In order for a molecule to be stable, it must contain the right amount
of electrons. If the molecule loses an electron when it isn't supposed
to, it can turn into a free radical.
Free radicals are unstable, electrically charged molecules in the cells,
that can react with other molecules (like DNA) and damage them.
They can even form chain reactions, where the molecules they
damage also turn into free radicals.
So antioxidant work as a doner of electron to free radical and
neutrilize it ,so free radical become stable and antioxdant does not
become a free radical (unstable molecule).

15. Levels of antioxidant action:
– Antioxidants, capable of neutralizing free radicals or their actions at the following level :
– 1-Prevention 2- Interception 3-Repair
– Preventive antioxidants: Attempt to stop the formation of ROS. These include superoxide
dismutase (SOD) that catalyses the dismutation of superoxide H202 and catalase that breaks
it down to water.
– Interception of free radical : Is mainly by radical scavenging, while at the secondary level
scavenging of peroxyl radicals are effected. The effectors include various antioxidants like
vitamins C and E, glutathione, other thiol compounds, carotenoids, flavonoids, etc.
– At the repair and reconstitution level , mainly repair enzymes are involved e.g ligase enzyme.

16. Types of antioxidant
– There are three types of antioxidant found
In nature or in a dietry supplement :
1) Antioxidant enzyme.
2) Antioxidant from vitamins E and C.
3) Phytochemical antioxidant.
2 and 3 (Natural sources of antioxidant).

17. 1) Antioxidant enzyme :
– Superoxide dismutase:is an enzyme that alternately catalyzes the dismutation (or partitioning) of
the superoxide (O2
−) radical into either ordinary molecular oxygen (O2) and hydrogen
peroxide (H2O2).
– Has two types: Cu,Zn-SOD in cytosol / Mn-SOD in mitochondria.
– Note : Dismutation :is a specific type of redox reaction in which an element from a reaction
undergoes both oxidation and reduction to form two different products.
– Cu2+-SOD + O2
− → Cu+-SOD + O2 (reduction of copper; oxidation of superoxide)
– Cu+-SOD + O2
− + 2H+ → Cu2+-SOD + H2O2 (oxidation of copper; reduction of superoxide)
– Catalase: is a common enzyme found in nearly all living organisms exposed to oxygen (such
as bactria, plants, and animals). It catalyzes the decomposition of hydrogen peroxide
to water and oxygen.It is a very important enzyme in protecting the cell from oxidative
damage by reactive oxygen species (ROS).
– 2 H2O2 → 2 H2O + O2

18. – Glutathione peroxidase :is the general name of an enzyme family
with peroxidase activity whose main biological role is to protect the organism
from oxidative damage.The biochemical function of glutathione peroxidase is
to reduce lipidhydroperoxidase to their corresponding alchole and to reduce
free hydrogen peroxide to water.
– The main reaction that glutathione peroxidase catalyzes is :
– 2GSH + H2O2 → GS–SG + 2H2O
– Glutathione reductase:catalyzes the reduction of glutathione disulfide (GSSG) to
the sulfhydryl form glutathione(GSH), which is a critical molecule in
resisting oxidative stress and maintaining the reducing environment of the cell.
– GS–SG + NADPH + H+ → 2 GSH + NADP+.
– preventing oxidative stress in human cells. It can act as a scavenger for hydroxyl radical, singlet oxygen,
and various electrophiles.

19. Natural
antioxidant:

20. Some antioxidant and their mode of
action

21. Thank you