Antioxidants

Question 1

What are Reactive Oxygen Species?

Answer 1

toxic by-products of oxygen metabolism

Question 2

Name some ROS:

Answer 2

Superoxide
Hydrogen peroxide
Hydroxyl radical
Nitric oxide

Question 3

What is Oxidative Stress?

Answer 3

production of ROS is greater than the antioxidant defenses can consume them

Question 4

Ischemia-Reperfusion Injury

Answer 4

most tissue damage occurs on re-exposure to oxygen after cardiac infarct or other ischemic event

Question 5

ROS are believed to be involved in what diseases?

Answer 5

Cancer - oxidative damage to DNA
Atherosclerosis - ox of low density lipoprotein and its uptake by macrophages
Alzheimer’s disease - neuronal death from elevated NO and/or mitochondrial dysfunction
Aging - progressive decline in mitochondrial function

Question 6

Vitamin E is what type of Antioxidant?

Answer 6

lipophilic
functions as a chain-breaking antioxidant that prevents propagation of the lipid carbon centered radicals of the Fatty Acid residues of membranes

Question 7

What foods contain Vitamin E?

Answer 7

grains
wheat germ
nuts
vegetable oils

Question 8

Vitamin E may contain a variety of ___ and ___ .

Answer 8

Tocopherols (w saturated side chains)

Tocotrienols (w 3 double bonds in side chains)

Question 9

The tocopherol with the highest activity and is often called “natural” vitamin E

Answer 9

alpha-tocopherol

Question 10

Absorption of Vitamin E:
where?
where does it go?
in what form?

Answer 10

Absorbed in the intestine and transferred to the liver

Chylomicrons (plasma lipoproteins)

Question 11

Does Vitamin E protect against heart disease?

Answer 11

No good evidence.

Supplements not currently recommended.

Question 12

Problem with ingesting too much Vitamin E?

Answer 12

Can compete with Vitamin K absorption (potential problem with anticoagulants).
The TUL is 1000 mg/day so other than that it is not very toxic despite being fat soluble.

Question 13

Tolerable upper limit of Vitamin E

Answer 13

1000 mg/day

Question 14

Recommended Dietary Allowance (RDA) for Vitamin E

Answer 14

15 mg/day

Question 15

So, Vitamin E is important for protecting molecules in what type of environment? Hydrophilic/phobic
Example of where…

Answer 15

Hydrophobic environments

CNS

Question 16

Vitamin C is an example of what type of Antioxidant?

What makes it special?

Answer 16

Hydrophilic

Can be oxidized to other forms of the vitamin making it the major hydrophilic antioxidant

Question 17

Relationship between Vitamin C and Vitamin E?

Answer 17

Vitamin C returns Vitamin E to its reduced form, so indirectly impacts the oxidation of the membrane

Question 18

Evidence for the benefits of Vit C?

Answer 18

Lowered markers of…
DNA oxidation
membrane oxidation

Some evidence of lowering risk of...
heart disease
cancer
cataracts
protection for smokers

Question 19

Vitamin C is also important for ____ synthesis, deficiency results in ____ as seen in pirates.

Answer 19

collagen synthesis
scurvy

also, deficiency causes slow wound healing

Question 20

Another important role of Vit C, is that it aids in the absorption of ____

Answer 20

Iron

by reducing ferric iron to ferrous iron

Question 20

Toxicity of Vitamin C?

Answer 20

Low - some advocate massive doses (30-60 times RDA of 75 mg/day)

Question 21

What foods are good sources of Vit C?

Answer 21

citrus fruits, tomatoes, green peppers, broccoli, and other vegetables

Question 22

Antioxidant Enzymes include (3):

Answer 22

Glutathione peroxidases
Superoxide dismutases
Catalases

Question 23

Glutathione peroxidase..action

Answer 23

catalyzes the reduction of hydrogen peroxide by glutathionine
(oxidized glutathionine is red by glutathione reductase which uses NADPH)

Selenium - at the active site, essential but not an antioxidant itself

Question 24

Selenium is found in two antioxidant enzymes:

Answer 24

Glutathione peroxidase | Thioredoxin reductase

Question 25

So Selenium is an essential Antioxidant?

Answer 25

No. Essential but not an Antioxidant. Required for: Glutathione peroxidase Thioredoxin reductase

Question 26

Superoxide dismutase

Answer 26

dismutation of superoxide -> hydrogen peroxide + O2 mammals have at least two isozymes

Question 27

Catalases

Answer 27

dismutation of hydrogen peroxide -> water and oxygen a hemoprotein found in peroxisomes (normally the site of most, if not all, H2O2 generating rxns)

Question 28

Flavonoids and Flavones are what type of Antioxidant?

Answer 28

Hydrophilic antioxidants | Just like Vitamin C

Question 29

What foods are Flavonoids and Flavones found in?

Answer 29

green tea, red wine, cocoa

Question 30

What potential benefits do Flavonoids and Flavones have?

Answer 30

possibly reducing cardiovascular disease and cancer

Question 31

What are some of the effects of Selenium?

Answer 31

Prevention of purine oxidation (measure of purine oxidation = 8-oxoguanine production) Selenomethionine in thioredoxin activates the tumor suppressor protein Grave's Disease patients by preventing deterioration of vision

Question 32

Describe the two Isozymes of Superoxide Dismutase.

Answer 32

1) Cytoplasmic: active site copper and zinc ----genetic deficiency in Cu/Zn enzyme =>amylotrophic lateral sclerosis (Lou Gehrigs) 2) Mitochondrial: active site manganese. Note: Extracellular forms may also exist.

Question 33

Vitamin ___ would be expected to be most effective against ROS found in the cytosol while Vitamin ___ would be useful for neutralizing ROS that are located in membranes.

Answer 33

Vitamin C - cytosol (hydrophilic) | Vitamin E - membrane (hydrophobic)

Question 35

T / F - Metal ions promote oxidation.

Answer 35

Iron promotes oxidation of lipids and other compounds. But are more examples of metal ions that promote reduction by helping antioxidant enzymes. Ex: selenium (involved with glutathione peroxidase) copper and zinc (which are components of superoxide dismutase) Other metal ions, like Ca or Mg, probably have no effect one way or the other.

Question 36

What is 8-Oxoguanine?

Answer 36

An oxidation product of the base guanine. Results from catabolism of DNA/RNA followed by Oxidation. Marker of DNA Oxidation

Question 37

What is Dismutation?

Answer 37

Dismutation is a molecular rearrangement in which one part of a molecule is oxidized and another is reduced. Ex; superoxide dismutase

Question 38

Benefits of Antioxidant Supplementation?

Answer 38

No evidence; But evidence for the benefit of Antioxidant rich food is real.

Question 39

What food contains more Antioxidants than any other fruit or vegetable?

Answer 39

Blueberries