Download MBBS Vitamin E Lecture PPT

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)


STAY HOME STAY SAFE

This post was last modified on 30 November 2021