2. Vitamin D
Vitamin D is a group of steroids (D1, D2, D3,
D4 and D5) chiefly occuring in animals but also
in plants and yeast.
The physiologically active forms are D2 and D3.
Vitamin D posses cyclopentanophenanthrene
ring in the structure.
3. Provitamins D are ergosterol (plant) and 7
dehydrocholesterol (in skin). These on UV-
irradiation or sunlight exposure give rise
ergocalciferol (D2) and cholecalciferol (D3)
respectively.
4.
5. Sources
Richest sources are liver and viscera of fish.
Other sources are egg and cheese.
Its vitamin D content can be incresed by UV
irradiation.
6. Daily requirements
• Infants and children- 400IU
• Adults- do not require under normal conditions.
• During pregnancy and lactation- 500-600 IU
(1 IU= activity caused by 0.025 μg of calciferol)
7. Physiological functions
Vitamin D has a direct effect on calcification.
It increases calcium and phosphorus absorption
from intestine.
It has a role in citrate metabolism as
administration of vitamin D increases citrate
contents of blood, bones, kidney, heart and small
intestine.
Vitamin D is involved in renal handling of
phosphorus.
8. Deficiency diseases
Rickets in children
• Ricket is characterised by faulty calcification of
bones due to low vitamin D content of body, a
deficiency of calcium and phosphorus in diet or
due to both.
• The features are; infant becomes restless, fretful
and pale with flabby and toneless muscles.
• Abdomen is distended and there is extension and
widening of epiphysis at growing points.
9. Osteomalacia in adults
• Disease is limited to female sex.
• The bones specially pelvic girdle, ribs and
femora become soft, painful and deformed.
• Softening of bones is primarily due to deficiency
of vitamin D and to a lesser extent to the
deficiency of calcium.
10. Vitamin E (antisterility factor)
Vitamin E activity is attributed to a series of
compounds- the tocopherol (Tokos-child birth,
pherein – to bear).
There are 4 such substances- α, β, γ and δ.
All are isoprenoid substituted 6-hydroxy
chromanes.
D- α-tocopherol has widest natural distribution
and greatest biological activity.
11.
12. Sources
Rich source of vitamin E are milk, egg, muscle
meat, fish, cereals and leafy vegetables.
Daily requirements- 30mg
Functions
vitamin E act as natural antioxidant.
Vitamin E and selenium act synergistically and
reduce requirement for each other in the body.
It prevent hepatic necrosis produced by lack of
S containing amino acids in dietary proteins.
13. Deficiency
• In huamn deficiency causes muscle weakness,
muscular dystrophy, fragility of erythrocytes
with mild anemia.
In animal deficiency causes resorption of
foetus in females and atrophy of spermatogenic
tissue leading to permanant sterility in male.
14. Vitamin K
Vitamin K are napthoquinone derivatives with
polyisoprenoid side chains.
Fat soluble vitamin K1 (phylloquinone) and K2
(menaquinione) are naturally occuring.
Water soluble K3 (menadione) is synthetic and
used clinically.
15.
16. sources
The chief source of vitamin k are liver, green
leafy vegetables, peas, cereals, egg yok and
cheese. Fruits are poor sources.
Functrions
Vitamin K is required for the biosynthesis of
blood clotting factors II, VII, IX and X.
All are synthesised in the liver initially as
inactive precursor proteins.
17. Biologically active clotting factors involves post
translational modification of glutamate to γ-
carboxy glutamate residue mediated by a
specific vitamin K dependant carboxylase.
