vit E Flashcards
Generation of free radicals in oxidative stress is associated with damage to what cellular structures
lipid peroxidation
protein oxidation
DNA and RNA oxidation - (Attacking DNA prevents cell from surviving)
mitochondrial abnormalities
what type of vitamin is vit C
lipid soluble
vit C protects lipids from what
free radicals and oxidative stress
explain lipid peroxidation
Free radical removes hydrogen from an unsaturated carbon atom on lipid (e.g. membrane phospholipids) to form lipid radical
LH + X* L* + XH
The lipid radical reacts with molecular oxygen to form a peroxyl radical, LOO*
Lipids with double bond are vulnerable to attack these are found in membranes
The peroxyl radical can react with other membrane lipids to form a lipid hydroperoxide and another lipid radical
LOO* + LH LOOH + L* i.e. self-perpetuating cycle
Lipid hydroperoxides can form toxic, unsaturated aldehydes (not free radicals but continuously made by this cycle and can eventually cause damage to tissue) e.g. 4-hydroxy-nonenal
Oxidative stress has resulted in this cycle and so higher levels of these unsat aldehydes which toxic to neurons, neurons die and cause damage such as aszhymers
explain vitamin E, alpha tocopherol
Can reduce lipid peroxidation
LOO* + TOH LOOH + TO*
- TOH = tocopherol – this is more stable and not a lipid radicals so breaks cycle
- LOO = lipid peroxide radicals
Tocopherol radical more stable and does not regenerate lipid peroxides i.e. cycle is broken
Vitamin C can recycle tocopherol radical to form regenerated tocopherol, so it can be used to break more cycles by moping up these free radicals
AH2 + TO* AH- + TOH
explain the regeneration of ascorbate
Can be regenerated by several mechanisms, including niacin and glutathione
2AH- + NADH 2AH2 + NAD+ 2AH- + 2GSH 2AH2 + GSSG
First reaction is reduction of ascorbate to its reduced form
Second reaction is similar but uses glutathione
These are used to regenerate ascorbate
explain the vitamin E structures
alpha-tocopherol has methyl groups at R1, R2 and R3- highest activity
beta R1 + R3, gamma R2 + R3, delta R3
Tocopherol - It’s a saturated straight chain . This one has higher activity. The alpha version of this has greatest activity
Tocotrienols are unsaturated so have double bond on straight chain
Beta tocopherol has methyl groups at different R groups
Most biologically active form is alpha form
tocopherols and tocotrienols are mirror images but the trineols have a double bond
sources of vit E
plant oils
milk
wholemeal flour
wheat germ
wholemeal bread
meats
seeds and nuts
fruit and veg
Vit e is lipid soluble so its expected to be associated with oils, particularly plant oils
Animal products have less high a source
what are the vit e requirements determined by
by PUFA intake
(6 % energy intake)
what are the vit e RNIs for men and women
0.4 mg a-tocopherol eq./g PUFA intake, so RNI:
7 mg/d in males
5 mg/d in females
what is the uk intake range of vit c
2-27 (average of 10) mg/d
diets low in what cause vit e requirements to be greater
low-selenium (antioxidant nutrient) diets
higher vit e consumption is required for diets high in what
poly unsat fatty acid intake
