This document discusses reactive oxygen species (ROS), also known as free radicals, which are highly reactive molecules that can damage cells. ROS are produced naturally in the body during energy production but also by environmental and lifestyle factors. They are implicated in many diseases. The body protects itself from ROS damage through antioxidant enzymes like superoxide dismutase and glutathione peroxidase, and by obtaining antioxidants from foods, which help neutralize free radicals. Aging leads to declines in these protective antioxidant defenses.

1. Antioxidants & Free radicals

3. What are Reactive Oxygen
Species?
 ROS also known as Free oxygen radicals
 Any molecule with an unpaired electron
 Extremely chemically reactive
 Damage cell membranes
 Responsible for more than 100 human diseases
 Aging, cancer, heart attacks, stroke and arthritis
 Some beneficial effects

4. How are ROS Formed?
 Primary source is our body during energy
production
 Environmental contaminants
 Ionizing and ultraviolet radiation
 Prolonged low blood flow states
(atherosclerosis, heart attacks and stroke)
 Diet (fatty and processed foods)
 Low levels of antioxidants

5. Protection from ROS
Damage
 Superoxide dismutase
 Catalase
 Glutathion
 Antioxidants in diet
 Supplementation

6. Aging and Effect on Antioxidant
Enzymes
 Significant decline in SOD
 Significant decline in catalase and glutathione
 Significant decline in energy production
 Cellular, tissue and system aging and failure

7. Scientific Support for
Antioxidants
 Animals with longer life spans have higher
antioxidant levels
 Dietary increase in antioxidants increase
life span
 Caloric restriction (reduces ROS
formation) leads to significantly increased
life span

8. Questions asked
 What are free radicals?
 Types of free radicals
 Sources of free radicals
 Oxygen metabolism
 Discussion on oxidative damage and
oxidative stress
 What is antioxidant?
 Natural free radical defense systems
 What are Phytochemicals?

9. Nutrients Non-nutrients
Energy, building
materials
Factors regulating
metabolism
Lipid Protein Carbo-
hydrate
Vitamins Minerals
EFA &
non-EFA Glucose
Water
Phyto-
chemicals
•pigments
•Antioxidants
Fibers
Other food
components
Food
GSH
Cys
Functional food
or Neutraceuticals
C, E, b-Car
Zn, Se
EAA &
non-EAA

10. Free radical-Mediated
Diseases
 Diseases of the old -
Chronic and degenerative diseases
(diabetes, cataracts, Alzheimer’s disease, cancers,
cardiovascular disease, and aging)
 Diseases of the young and innocent -
Acute and immature diseases
(Eyes: retinopathy of prematurity, Lung:
bronchopulmonary displasia, Brain: cerebral pulsy,
Pancreas: Type 1 diabetes)

11. What are free radicals?
 Any molecule containing one or
more unpaired electrons

12. Types of Free Radicals
 Reactive Oxygen Species (ROS) -
 Reactive Nitrogen Species (RNS) - NO.
 Reactive Metabolites or Intermediates
- metabolic activation of drugs, toxins,
pollutants, cigarette smokes, etc.

13. Reactive Oxygen Species (ROS)
 Superoxide (O2
.-)
 Hydrogen Peroxide (H2O2)
 Hydroxyl Radical (OH.) - product of
Fenton reaction catalyzed by free Fe and Cu
 Singlet Oxygen (1DgO2) - oxygen at an
excited state, requiring photosensitizers and
photons

14. Sources of oxygen free radicals
 In mitochondria:
- generation of energy - ATP
- glucose, fatty acids, amino acids
- O2 2H2O
4e-
- leakage of O2
-. (superoxide)
H2O2 (hydrogen peroxide)

15.  In Smooth Endoplasmic Reticulum
(microsome)
- detoxification (cytochrome P-450s)
- toxins, drugs and xenobiotics
- O2 + RH R-OH and H2O
- leakage of O2
-.
- metabolic activation - X.

16.  In Peroxisomes
- containing oxidases for degradation of
various substrates
- glucose, amino acids, xanthine, etc.
- requires O2
- byproduct is H2O2

17.  In Cytoplasm
- nitric oxide (NO.) production from
Arginine
- functions as a biological messenger
- in brain, vascular endothelial cells, and
macrophages
- NO. + O2
-. ONOO. (peroxynitrite)

18. NO: a Biological Messenger
 NO is a neurotransmitter (brain- bNOS)
 NO regulates blood pressure (vascular
endothelial cells- eNOS)
 NO is a cytotoxic agent (macrophages-
iNOS)

19.  Production of Singlet Oxygen
- photosensitizers in the biological system
(bilirubin, riboflavin, retinal, porphyrin)
- requires light , O2 and photosensitizers
- chlorophyll in photosynthesis
- photodynamic therapy

20. Antioxidants
 Prevents the transfer of electron from O2
to organic molecules
 Stabilizes free radicals
 Terminates free radical reactions

21. Free Radical Defense System
 Antioxidant Enzymes
 Antioxidant Quenchers
 Antioxidant from
Foods – nutrients/non-
nutrients

22. Antioxidant Enzymes
 Superoxide Dismutase (SOD) – to get rid
of superoxide produced from electron
transport chain, the product is hydrogen
peroxide.
 MnSOD (mitochondria).
 CuZn SOD (cytosol).

23. Oxygen Radical Defense
Enzymes
O2•¯ H2O2 H2O + O2
Mn SOD Catalase
GSH
Peroxidase
CuZnSOD
OH•
Fe2+

24. Antioxidant Enzymes - 2
 Glutathione Peroxidase (GSH PX) – to
get rid of hydrogen peroxide (H2O2) and
some lipid peroxide. It requires reduced
glutathione (GSH) as substrate and
produces oxidized glutathione (GSSG)
as product. A cytosolic enzyme.

25. Functions of GSH-dependent
Enzymes
L-OH
H2O GSSG NADPH
L-OOH
H2O2
GSH NADP+
X.
GSX
X-Mercapturic Acid
GSH Px
GSH-TR
GSH--Rx

26. Glutathione
 GSH is a tripeptide, g-glutamyl-
cysteinyl-glycine
 The sulfur atom of the cysteine
moiety is the reactive site which
provides electrons
 GSH is stable because the g bond
in glutamyl-cysteine (not the a
peptide bond) is resistant to cellular
peptidases

27. Glutathione
 GSH is the most abundant non-protein thiol in
mammalian cells
 GSH is a substrate for two enzymes that are
responsible for detoxification and
antioxidation.
 Other physiological roles including cysteine
storage and transport, prostaglandin
metabolism, immune function, cell
proliferation and redox balance

28. Glutathione Synthesis
Protein
Methionine
Cysteine
Glutamate
g-Glutamylcysteine
Glycine

29. Antioxidant Enzymes - 3
 Catalase –to get rid of hydrogen peroxide
produced in peroxisome.

30. Antioxidant Quenchers
 Cellular proteins which chelate pro-oxidant
minerals (iron and copper or others)
 Transferrin – iron transport protein
 Ferritin – iron storage protein
 Metallothionein – minerals and heavy
metals (Zn/Cu/Cd/Hg)
 Ceruloplasmin – copper transport and
storage

31. Antioxidants From Food
 Antioxidant nutrients – vitamin E, vitamin C,
(vitamin A?), beta-carotene
 Phytochemicals – antioxidants from plants