Antioxidants Dr. Goueli 5/12/14

Question 1

Superoxide Dismutase

Answer 1

• converts superoxide anion to hydrogen peroxide and O2 (called dismutation)
• called the primary defense against oxidative stress because superoxide is a strong initiator of chain reactions
• activity is increased by chemicals and conditions, such as hyperbaric oxygen, which increase superoxide production
• implicated in familial ALS (5-10% of total ALS)***

Question 2

Vitamin E (alpha-tocopherol)

Answer 2

• Most widely distributed antioxidant in nature
• Lipid-soluble antioxidant vitamin that functions predominantly to protect against lipid peroxidation in membranes
• There are several tocopherols; they differ in their methylation pattern

-alpha-tocopherol is the most potent antioxidant and present in the largest amounts in our diet
Efficient antioxidant and nonenzymatic terminator of free radical chain reactions

• Has little pro-oxidant activity; would otherwise propagate the free radical chain reaction
• When Vitamin E donates an electron to a lipid peroxy radical, it is converted to a free radical form that is stabilized by resonance
• Has a greater tendency to donate a second electron and go to fully oxidized form than to be reduced after donating its first electron

Question 3

Vitamin E deficiency

Answer 3

• Uncommon
• Hemolytic anemia due to fragility of RBCs
• Imbalance
• Myopathy
• Neurologic deficits due to degeneration of neurons
• Found in corn, nuts, olives, green leafy vegetables, vegetable oils, wheat germ, egg yolks and liver.

Question 4

Vitamin C

Answer 4

Oxidation-reduction coenzyme that functions in collagen synthesis and other reactions, and plays a role in free radical defense

Reduced ascorbate can generate the reduced form of vitamin E by donating electrons in the redox cycle

Water soluble and circulates unbound in blood and extracellular fluid, where it can access lipid-soluble vitamin E present in membranes and lipoprotein particles

Can react with ROS, hypochlorite, nitric dioxide, peroxyl radicals

Question 5

Vitamin C deficiency

Answer 5

• Impaired wound healing
• Bleeding ecchymoses
• Swollen gums
• Anemia
• Enlargement and keratosis of hair follicles
• lethargy
• depression
• Scurvy***
• Found in citrus fruits, green peppers, strawberries, broccoli and sweet and white potatoes

Question 6

Vitamin A deficiency

Answer 6

• Number 1 cause of non-accidental blindness worldwide
• Night blindness***
• Follicular hyperkeratosis
• Xeropthalmia
• Found in eggs, meat and dairy products. Beta-carotene, a precursor, comes from green leafy, vegetables and intensely colored fruits and vegetables.