the balance between free radicals and antioxidants is a necessity for proper physiological work in the body, but when the difference between them produces a so-called oxidative stress

1. Wael
AL-HARBI
@Wael_S_Alharbi

2. INRTODUCTION
General
Antioxidants are chemical compounds that have the ability to inhibit and
slow down the oxidation processes that occur during biochemical
reactions. They are involved in the defense mechanism against diseases,
caused by free radicals .
Free radical is known to have an electron or a lot in a single case. This
makes it either able to accept an electron or give an electron, either
oxidized or reduced .

3. General
Therefore, free radicals are less stable and thus to achieve a more stable condition free
radical can interact with other compounds such as proteins, lipids, carbohydrates, and
nucleic acids . Because of these interactions and links with other compounds, the free
radicals destroy the biological systems of the body, and this is through the chemical
reactions that are created within the body leading to many diseases such as cancer,
atherosclerosis, heart diseases, aging, diabetes, and cirrhosis.
One of the most important of these free radicals is
what is known as reactive oxygen species (ROS)
because the main element in all living functions of
the living cell is (O2).
It is responsible for most reactions in the
respiratory system and cellular interactions. Types
of ROS include the hydroxyl radical, peroxide,
hydroxyl ion, the superoxide anion radical,
hydrogen peroxide and singlet oxygen.

4. The main cellular sources of reactive
oxygen species in the body of an
organism is what is known as
mitochondria.
There are also types of free radicals
known as interactive nitrogen species
(RNS), which are compounds derived
from nitric oxide (•NO) and superoxide
(O2•−) .This type of RNS is produced by
enzymatic reactions NOS2 and NADPH
oxidase respectively. Interactive nitrogen
species (RSN) also work with reactive
oxygen species (RON) to destroy and
destroy the living cell and are therefore
often collectively labelled as a ROS/RNS.

5. But although these free radicals can be destroyed by
the antioxidants produced by the body of the organism,
they are not enough to destroy them completely.
Therefore, antioxidants are needed to help the body
destroy free radicals . Thus, the antioxidants play the
very important role to keep the human body against
harm by reactive oxygen species. Endogenous
antioxidants are enzymes, for example, glutathione
nonenzymatic, superoxide dismutase, catalase or
peroxidase compounds, for example, metallothionein's,
bilirubin. Once endogenous factors cannot ensure a
complete protection of the organisms against the
reactive oxygen species, the need for exogenous
antioxidants increases, as pharmaceutical products or
nutritive supplements, which contain as active principle
an antioxidant compound. The most important
exogenous antioxidants, vitamin C, β-carotene, vitamin
E, flavonoids, and gamma tocopherol.

6. Oxidative stress can be defined as a phase in which free radicals are more than
antioxidant systems in the body of the organism causing a loss of balance. Therefore,
oxidative stress is classified as harmful to the body because when free radicals are
more than antioxidants they are able to attack biological systems, causing lifestyle-
related diseases as mentioned earlier. However, oxidative stress may be useful in the
short term. For example, the immune system in the organism can use excess free
radicals of the reactive oxygen species to eliminate pathogens