Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Vitamin E Lecture PPT
INTRODUCTION
? Vitamin E is chemically known as tocopherol (Greek:
tokos=childbirth, pherin =to bear and ol=alcohol)
? anti-infertility Vitamin
? Infertile animal + vitamin E conception of
animal
? Vitamin E is lipid soluble antioxidants in cell
membranes, and is important in maintaining the
fluidity of cell membranes.
? Structure of Vitamin E was elucidated by Paul Karr (
Noble prize-1937)
CHEMISTRY
Vitamin E a name given to a group of Tocopherols and
Tocotrienols
? tocopherol (5,7,8 trimethyl tocol)
5
Structure of a-tocopherol (various tocopherols differ
in the substitution of methyl groups on chromanol
nucleus).
.
? Chemically
it
is
a
substituted
hydroxychromane derivative or methylated
tocols
? 8 derivatives of Tocopherols identified as
,,, Tocopherol etc. out of which -
tocopherol is most active physiologically.
? OH group of Tocol is responsible for
antioxidant property of Vitamin E
? Tocotrienols have 1-50% activity of activity of
Tocopherols
ABSORPTION, TRANSPORT AND
STORAGE
? It is absorbed along with other fats and needs the
help of bile salts.
? Tocopherol is absorbed and transported as chylo
microns.
? In the liver, it is incorporated into lipoproteins
(VLDL and LDL) and transported
? It is stored in adipose tissue, liver and muscle.
? During catabolism, the chromane ring and side
chain may be oxidized and excreted in bile after
conjugation with glucuronic acid
Don't forget
.
TISSUE DISTRIBUTION
? All cell membranes including mitochondrial
membrane and endoplasmic membrane.
? Retina is specially rich in vitamin E.
? Plasma levels are 0.5 -1 mg/dl
BIOCHEMICAL ROLE
A. Antioxidant Role
? It is a potent natural antioxidant vitamin.
? It is a chain breaking and peroxyl-radical
scavenging antioxidant
? It protects most lipophilic molecule
susceptible to oxidant injury like PUFA, and
phospholipid having PUFA, present in cell
membranes, lipoproteins, RBC, mitochondrial
membrane, retina etc.
.
? It acts as an antioxidants by donating a hydrogen
radical H. and terminating the chain reaction of
fatty acid peroxidation.
? Vitamin E itself becomes phenoxy radical which
is relatively more stable.
? Its further fate is two fold:
1. It is reduced by vitamin C back to original form.
The oxidized vitamin C is maintained in reduced
form through glutathione and NADPH via the
HMP pathway.
.
? The phenoxy radical may undergo a series of
rearrangement
involving
oxidation
of
chromane ring and side chain. This is then
conjugated with glucuronic acid and excreted.
.
2.Synergistic action with glutathione peroxidase
and sparing of selenium
? Lipid peroxides produced by oxidation of
lipids are neutralized by glutathione peroxidase
as a second line of defence.
? vitamin E acts synergistically with Selenium
which is a cofactor of antioxidant enzyme
Glutathione peroxidase that destroys free
radicals .
? Vitamin E can spare requirement of Selenium
,and vice versa.
Reduction of lipid peroxide by
glutathione peroxidase
3. Anti ? atherogenic effect:
? Oxidation of LDL is an initial and critical
event in the development of atherosclerosis.
Vitamin E is known to prevent this oxidation.
Hence, vitamin E has anti atherogenic role .
4. Ant sterility role
? Prevents sterility and closely associated with
reproductive functions
? maintains germinal epithelium of gonads
? Anti sterility role in humans is doubtful.
.
5. Maintaining the structural and functional
integrity of cells and organs. In that sense, it is
said to have anti ? aging effect.
6. It protects the RBC from hemolysis by
oxidizing agents (e.g. H2O2) and thus helps in
maintaining RBC membrane integrity.
7. Enhances activity of aminolaevulinic acid
(ALA) synthase and ALA dehydratase
Enhances heme synthesis
8. Required for cellular respiration through
electron transport chain ( stabilizes coenzyme
Q)
9. Vitamin E encourages .skin healing and reducing
scarring effect after injuries such as burn- extensive
use in skin creams and lotions.
10. It is required for proper storage of creatine in skeletal
muscle
11..It protects the liver from toxic compounds such as
carbontetrachloride
12.It works in association with vitamin A,C and beta-
carotene, to delay the onset of cataract
13.It is said to be beneficial in Alzheimers disease, skin
disorders, cancers
14.Trace amount of vitamin E ( hydroquinone),Gallic
acid and alpha naphthol are added in commercial
preparation of fat and oils to prevent oxidative
rancidity
Vitamin E Deficiency
? Blood levels:
levels below 5 ?g/ml are
suggestive of vitamin E
deficiency.
? Causes :
1. Dietary deficiency
4. Malabsorption
2. Obstructive jaundice
syndrome
3. Patients with cystic
5. Hypolipoproteinemia
fibrosis & chronic liver
diseases
6. Very low birth weight
infants
Manifestation of vitamin E Deficiency
1. Anaemia due to RBC hemolysis because of
the increased membrane fragility.
2. Neurological deficiency such as delayed
milestone in premature infant, i.e. late start of
standing, walking, crawling
3. Degenaration of post. Spinal column tract and
spinocerebellar tract causing decreased
vibration sense, demyelination of nerves,
cerebellar ataxia
Manifestation of vitamin E Deficiency
4 . Retinal pigmentation degeneration
5. Retrolental fibroplasia (RLF):a neuropathy
observed in premature infants with low birth
weight due to poor placental transfer of
Vitamin E .
6. Muscular weakness & creatinuria.
.
.
RDA
? Adults - 8 -10 mg/day
? Pregnancy & Lactation - 10 - 15 mg/day
? 15 mg of vitamin E is equivalent to 33 IU
? Pharmacological dose is 200-400 IU/day
Hypervitaminosis E
? Hypervitaminosis E : toxicity at doses above
1000 IU
? No toxic effects observed = LEAST TOXIC
fat soluble vitamin
? Tendency of hemorrhage.
? Neurological symptoms.
"Vitamin in search of a disease".
Clinical use of vitamin E
1. Fibrocystic breast diseases
2. Intermittent claudication ( episodes of
tingling, numbness and pain in the legs due to
ischemia ).
3. Patients at high risk of free radical ?mediated
injury ( prescribed along with other
antioxidants)
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This post was last modified on 30 November 2021