Download Introduction of Vitamins

Introduction of Vitamins
Teaching Policies
1. No sick leave certificates or other excuses
will be entertained for attendance.
2. Be aware of your attendance from the
beginning of the session.
3. The dates of mid exam once announced
will not be changed in any case.
4. There is no provision for make up exams.
5. First mid exam will be in the first class ()
of Sixth week ()of the session.
Definition
Vitamins are:
A. Natural micronutrient organic substances.
B. Having specific biochemical functions in the
human
body
(essential
for
health
maintenance).
C. Obtained from
microorganisms.
animals,
plants,
and
D. Required in very tiny (mcgs) and balanced
amounts.
E. Not made in the body (or not in sufficient
quantity)
Vitamins def. cont.
Exceptions are: Provitamins
β-carotenoids can replace Vit. A.
Tryptophan containing proteins can
replace Vit. B3 (niacin).
Exposure to sunlight can replace
Vitamin D.
Bacteria in the human colon synthesize
Vit. K2 menaquinones, which can be
absorbed.
F.
Their deficiency resulted in a specific
diseases.
Tips to Remember
They are necessary dietary factors, not
produced
by the body (except
vitamin D3).
They function as co-factor (regulator) of
metabolic reactions in the body.
Daily requirement of most vitamins is
around 1 mg.
Classification of Vitamins
Vitamins are classified by their biological and
chemical activity. Till now 13 vitamins are universally
recognized :
1- Fat soluble vitamins:
A. Vit. A (Retinol, Retinal, Retinoic acid)
B. Vit. D (Vit. D3: Cholecalciferol, Vit. D2:
Ergocalciferol)
C. Vit. E (α-Tocopherol)
D. Vit. K (Vit. K1: Phylloquinones,Vit. K2:
Menaquinones)
2-Water soluble vitamins:
(A) Vit. B group
B1 (Thiamin)
B2 (Riboflavin)
B3 (Niacin)
B5 (Pantothenic acid)
B6 (Pyridoxine)
B9 (Folic acid)
B12 (Cyanocobalamin)
(B) Vit. C : (l-Ascorbic acid)
(C) Vit. H: (Biotin)
Role of Vitamins in Metabolism
Vitamins have catalytic functions (co-factors) in
the metabolic reactions and do not act as
building substances (that is why the daily
requirement is very small).
Since each vitamin has very specific function in
metabolism, therefore, its deficiency will
adversely affect one or more biochemical
reactions in certain organs and very
characteristic deficiency symptoms will
appeared.
Cases of Vitamin Deficiency and Toxicity
(1). Avitaminosis: It is any disease caused by chronic or
long- term vitamin deficiency or caused by a defect in
metabolic conversion, such as tryptophan to niacin.
It leads to well defined symptoms e.g.
Xerophthalmia due to Vitamin A deficiency.
Rickets due to Vitamin D deficiency.
Pellagra due to Vitamin B3 deficiency.
Beriberi due to Vitamin B1 deficiency.
Scurvy due to Vitamin C deficiency.
(2). Hypovitaminosis: Resulted from inadequate supply of
one or more vitamins. It appears in the form of well
defined symptoms as skin changes, reduced vitality
and low resistance to infections.
(3).
Latent
hypovitaminosis:
A
case
of
unrecognizable deficiency symptoms but
immediately
appeared
under
sudden
stress or exposure to different environment.
(4). Hypovitaminosis due to Anti- vitamins:
Thiaminase in raw fish destroy Vit. B1.
Avidin in raw egg forming complex with
biotin (vitamin) (biotin – avidin) prevents
absorption of biotin.
Liatin in linseed oil is antagonist to Vit. B6.
5. Hypervitamninosis:
A case which develops only upon prolonged
use of excessive amount of vitamins.
EXAMPLES:
Hypervitaminosis D
Hypervitaminosis A
Usually this is caused by excessive
This occurs after large
over dosage of the vitamin. ingestion or over prescription of
prescribed medications such as
Symptoms include:
calcium with vit. D.
Headache
Symptoms include:
Abdominal pain
Polyuria
Nausea or vomiting
Vomiting
Lethargy
Constipation
Visual changes
Hypertension
Impaired consciousness
Seizures - can be fatal
Medicinal applications of Vitamins
Elimination of hypovitaminosis.
Treatment of some diseases.
Prophylaxis against some diseases.
1- Fat soluble vitamins
Vitamins
A
Medicinal applications
1. Lowered resistance to infections.
2. Dark-adaptation.
D
1. Prophylaxis and therapy of rickets.
2. Cases of bone atrophy.
3. Improves tooth consistency.
E
1. In cardiac, vascular and muscular disorders.
2. Fat with high levels of unsaturated fatty acids
absorption disorders.
K
1. Disorders of blood coagulation.
2- Water soluble vitamins
Vitamins
B1
Medicinal applications
1. Beri beri.
2. Nervous inflammations, neuralgias.
3. Cardiac dysfunction caused by alcoholism.
B2
1. Ariboflavinosis.
2. Photophobia and blurred vision.
3. Corneal vascularization and eye itching
B3
1. Pellagra.
2. Multiple B-complex deficiency syndrome.
B5
Dermatitis and seborrhea.
2- Water soluble vitamins
Vitamins
Medicinal applications
B6
1. Irritability and convulsion.
2. Hypochromic anemia.
3. Peripheral neuritis..
B9
Megaloblastic anemia.
B12
1. Juvenile pernicious anemia.
2. Gastrecotomy and celiac disease.
3. Long term drug therapy as neomycin.
4. Inflammatory lesions.
C
1. Scurvy.
2. Poor wound healing.
Cases of addition of Vitamins to food
1. Vitaminisation: Addition of vitamins to foods which
do not necessarily contain them naturally
(Addition of vitamins A and D to margarine).
2. Revitaminisation: Restoration of the original vitamin
contents of food that is lost during processing.
(Flour loss about 70% of its vitamin B content;
Skimmed milk must be revitaminized with
vitamins A and D as they removed on skimming
with fat).
3. Standardization: Compensation of seasonal variations
of vitamins in food (e.g. Milk must standardized
due to seasonal variation of vitamin A).
4. Enrichment: Addition of vitamins over the initial
natural level e.g. in Milk and flour.
5. Stabilization of food: Some food products show change
in color and taste due to oxidation by light and air.
Vitamins C and E ( water and fat soluble
antioxidants) are used to protect food from
oxidation and thus saving its nutritional value.
6. Curing agents: Na ascorbate is used to reduce the
amount of nitrite and nitrate ( food stabilizer).
7. Coloring of food products: The carotenoids (natural fat
soluble pigments and pro-vitamin A) and synthetic
carotenoids as: β-carotene, β-apo-8‘- carotenal, and
anthaxanthin are suitable for the coloring of
margarine and cheese.
Formulation of Vitamins
Formulation of vitamins must solve the following
problems:
1. Organoleptic characters
2. Providing accurate known quantities.
3. Stability.
(a) by addition of stabilizer (as antioxidants)
(b) synthesis of stable derivatives
4. Solubility.
transformation of water-soluble vitamins into
fat soluble derivatives or vice versa.
5. Administration route.
Vitamin- A
Extremely sensitive to oxidation by oxygen or light in
presence of metal, heat or moisture.
A. Stabilization for oily form of vit. A was achieved by:
 Ester formation as acetate or palmitate .
 Dissolving in vegetable oils.
 Addition of antioxidants.
 Using complexing agents.
B. Stabilization for water soluble derivatives :
Vitamin A dry powder:
 Deposit in gelatin as a carrier substance.
 Use of emulsion form.
Vitamin B1 (Thiamine)
 Inactivated
at neutral or alkaline pH
 Unstable in light and moisture
 Oxidizable.
1. Stable if protected from light and moisture.
2. Optimum stability at pH 3 - 4.5.
3. In the presence of vitamin B2 it is easily oxidized
in aqueous solution to thiochrome.
4. Thiamine.HNO3 is more stable than thiamine
HCl.
5. Protected dry preparation from humidity.
Vitamin B2 (Riboflavin)
Unstable in light, alkaline medium, and with
reducing agents – sparingly soluble in water –
unpleasant taste.
1.Use solubilizers e.g. nicotinamide or salicylic acid or
use Sodium salt of riboflavin-5'-phosphate
more water soluble.
2.For oral use, formulate it in coated form.
3. In aqueous solution it acts as oxidizing agent for
vitamins B1, C and folic acid.
Vitamin B5 (Pantothenic acid)

Very sensitive

Its Ca and Na salts are more stable in absence of
moisture.

The alcohol form (Pantothenol; panthenol;
Dpantothenyl alcohol) is used in aqueous
preparations.
Vitamin B12 (Cyanocobolamine)
Stable in acidic medium but unstable at high
temperature and in presence of vitamin B1, B3,
vitamin C, and some heavy metals.
Fat Soluble Vitamins
(Vitamin A and Carotenoids)
Vitamin A and Carotenoids
 Vitamin
A exists in animal foods in the form of
retinol esterified with fatty acids (usually as
retinyl palmitate).
 In
the body retinol can be oxidized to retinal or
retinoic acid which have 2 specific functions:
Retinal plays a central role in the
function of retina.
Retinoic acid helps regulate gene
expression and cell development.
The three compounds retinol, retinal and retinoic
acid are collectively referred as vitamin A.
Vitamin A is carried in the blood through a
retinol-binding protein (RBP). RBP is
synthesize in the liver.
Carotenoids (provitamin A) exist in plant foods.
The most common type is β-carotene which
can be absorbed as such or after splitting by
intestinal cells into vitamin A .
A large
carrot contains 15 mg of βcarotene which can supply enough vitamin A
for daily requirement.
Conversion of Carotenoids to Retinoids

Enzymatic
conversion
of
carotenoids occurs in liver or
intestinal cells, forming two
molecules of retinal and finally
retinol and retinoic acids.

Provitamin A carotenoids
 Beta-carotene
 Alpha carotene
 Beta-cryptoxanthin
Structure of different forms of Vitamin A
1
2
11
6
3
7
8
9
10
12
13
14
15
11
5
4
All-trans-Retinol
All-trans-Retinoic acid
All-trans-Retinal
11-cis-Retinal

Absorption of Vitamin A
Retinoids
Retinyl esters broken down to free retinol in
small intestine with the help of bile and
digestive enzymes.
 Once absorbed, retinyl esters reformed in
intestinal cells.
 90% of retinoids can be absorbed by this mode
of absorption.


Carotenoids
Absorbed intact but the absorption rate is
much lower.
 Intestinal cells can convert carotenoids in to
retinoids.

Source and Concentration of Vit. A and β-Carotene
Foods rich in vitamin A (retinol )
Beef liver
Cod liver oil (very rich source)
Egg
Serving size
100g
10g
1 whole
μg
9100
2550
110
Others: kidney, dairy products, butter, fortified margarine.
Foods rich in β- and other carotenoids
Carrot
Sweet potato
Spinach and broccoli
Serving size
1, large
1, large
100mg
Others: red palm oil apricots, peaches, melon, pumpkin.
μg Vit. A
810
920
460
Do you know?
Natural carotenoid supplements
micronutrients (Why?)
are
preferable
Answer:
1.They contain, along with β-carotene (the precursor
of Vit.A), a mixture of other important carotenoids,
including lutein and lycopene, which has additional
health benefits e.g:
Lycopene (red pigment of tomato) is a potent
antioxidant and decrease the risk of prostate cancer
and cataract.
lutein/zeaxanthin
(yellow
stereoisomeric
pigments in leafy vegetables) which give the yellow
colour to the macula lutea in the retina.
2. Less toxic than Vit. A.
lutein
Lycopene
Functions of Vitamin A
1. Vision:
Vit. A plays a central role in the
transformation of light energy into
nerve impulses which perceived by
brain as vision.
Deficiency: Night blindness
Role of Vitamin A in Vision

Retinal turns visual light into nerve signals in
retina of eye.

Retinoic acid required for structural components
(Cones and Rods) of eye :
 Cones in the retina
 Responsible for vision under bright lights
 Translate objects to color vision

Rods in the retina
 Responsible for vision in dim lights
 Translate objects to black and white vision
Mechanism of Action of Retinal in Night Vision
Mechanism of Action of Retinal in Night Vision
Rhodopsin, is a biological pigment in photoreceptor cells of
the retina that is responsible for the first events in the
perception of light. It is extremely sensitive to light,
enabling vision in low-light conditions.
Rhodopsin consists of the protein moiety opsin and a
reversibly covalently bound cofactor, 11-cis retinal.
The process of night vision occurs via G-protein coupled
receptors
called
opsins
which
contain
the chromophore (A chromophore absorbs and transmits
light energy) 11-cis retinal.
When
struck
by
photon,
11-cis
retinal undergoes photoisomerization to all-trans
retinal
which
changes
the
conformation
of
the opsin GPCR leading to formation of signal cascade
massages and sent to brain.
 Cessation of dark current takes place.
2. Skin and mucus membrane health :
Vit. A promotes proper growth of skin
epithelial cells and mucous membranes of
the respiratory, gastrointestinal,
and
genitourinary tracts.
Deficiency: Xerosis (mucus-secreting cells
are replaced by keratin producing cells)
dry skin and dry eye (xerophthalmia).
Xerophthalmia
Dry Skin
Stages of xerophthalmia: (Early signs of xerophthalmia include dry
conjunctiva and night blindness).
The first occurrence of Conjunctival xerosis (glistening white plaques
formed of thickened epithelium, usually triangular)
Corneal xerosis
(haziness or a granular pebbly dryness of the cornea)
Corneal
ulceration (keratomalacia)
dryness of conjunctiva and CEWG,
later2006of
cornea.
3. Immune system.
Vit.A increases resistance to infection by:
Maintaining the integrity of the skin epithelial cells
and mucous membrane barriers against
bacteria, viruses, and parasites.
Enhancing antibody production.
Increasing number and activity of macrophages, T
cells and natural killer (NK) cells and enhance
production of tumor necrosis factor-alpha (TNFα).
Deficiency: Impaired Immunity (frequent infections,
especially in respiratory system). In countries
where children are not immunized, infectious
disease like measles have relatively higher fatality
rates.
4. Hormone synthesis.
Vit. A is required for synthesis of steroid
hormones (corticosteroids, androgens and
estrogens) and production of human growth
hormone (GH).
5. Reproduction.
Vit. A maintains sperm count and sperm motility
in males. In females, deficiency is associated with
infertility and spontaneous abortion.
6. Cell growth and development.
7. Formation of red blood cells.
Vit. A plays an important role in mobilizing iron
stores to build new red blood cells.
Uses of Vitamin A in Prevention &
Therapy
1. Treatment of Night blindness.
2. Treatment of Skin /scalp Disorders: e.g Psoriasis,
Acne vulgaris, Dandruff, Eczema, Premature
aging of skin
3. Help in treatment of ear infections, conjunctivitis,
bronchitis, pneumonia, and infectious diarrheal
disease.
4. Cancer treatment: large doses of retinoic acid may
reduce growth and recurrence of certain forms of
skin cancer.
5. Cosmetics: Vitamin A derivatives are used as anti-
aging, being absorbed through the skin and
increases the rate of skin turnover, and a
temporary increase in collagen giving a more
youthful appearance.
6. Gastric ulcers: Vit. A maintain gastric mucus
production and reduce stress ulceration in
traumatized or burned patients.
7. Combination of iron + Vit. A may be effective than
iron alone in treating iron-deficiency anemia.
Some Products of Synthetic Retenoids (orally or topically)
13-cis-Retinoic acid (Tretinoin or Accutane)
Used in treatment of acne
Etretinate
Acitretin
Used in treatment of psoriasis
PEOPLE AT GREATER RISK OF
DEVELOPING VITAMIN A DEFICIENCY
1. Consumers of alcoholic beverage are liable to
vitamin A deficiency .
2. Patients taking some medications (birth control
pills, methotrexate, drugs sequestering bile acids
e.g. cholestyramine or chitosan).
3. Chronically ill people or recovering from surgery.
4. Patients under cancer treatment (radiation and
chemotherapy).
5. Cases that may impair Vit. A balance (chronic
diarrhea, cystic fibrosis, and kidney or liver
disease).
Vitamin A Toxicity
1. Infants and children are more susceptible than adults
to vitamin A toxicity.
2. Vitamin A is a teratogen and high doses (more than
10000 μg retinol) may produce birth defects, even
with exposure for 1week in early pregnancy.
3. Pregnant women should avoid excess intake of
vitamin A from supplements and from vitamin Arich foods,
such as liver (100 g contains
nearly 10000 μg retinol).
4. Daily dose should not exceed 2500 μg during
pregnancy or better replaced by cartenoids (their
conversion to Vit. A in the body is tightly
regulated, thus carotenes do not produce vitamin
A toxicity).
Signs and Symptoms of Vitamin A toxicity
1. Bone pain and joint swelling.
2. Nausea , vomitting and diarrhoea.
3. Dry skin and lips.
4. Hair loss.
5. Headache and blurred vision.
6. Enlargement of the liver and spleen.
7. Reduced thyroid activity.
8. High blood calcium
Drug interactions with Vitamin A
1. Other retinoid medications has higher risk of
cumulative toxicity with Vit. A supplement.
2. Use of mineral oil impairs absorption of all fat soluble
vitamins, including A.
3. Cholesterol-lowering drugs (e.g. cholestyramine) and
Aluminium-containing
antacids
inhibit
absorption of Vit. A.
4. Alcohol, barbiturates, caffeine, cortisone, tobacco,
and very high levels of vitamin E deplete Vit. A.
5. Over use of alcohol and Vit. A together increase the
possibility of liver damage.
THANX