ASCORBIC ACID (VITAMIN C)
Chemistry of Vitamin C
It is water soluble.
The structural formula of ascorbic acid closely resembles that of carbohydrates
Chemical name- Ascorbic acid
Biosynthesis of Ascorbic Acid in Animals
Most animals and plants can synthesize ascorbic acid from glucose.
Man, higher animals cannot synthesize ascorbic acid because of deficiency
of gulono lactone oxidase enzyme.
Dietary Sources of Vitamin C
amla, guava, lime, lemon and green leafy vegetables.
Requirement of Vitamin C
RDA is 75 mg/day
During pregnancy, lactation requirement is 100 mg/ day.
Metabolism of Ascorbic Acid
Ascorbic acid is readily absorbed from gastrointestinal tract.
The vitamin is excreted in urine.
Biochemical Functions of Vitamin C
Reversible oxidation-reduction
It can change between ascorbic acid and dehydroascorbic acid.
Hydroxylation of proline and lysine
Ascorbic acid is necessary for the post-translational hydroxylation of
proline and lysine residues
Hydroxyproline and hydroxylysine are necessary for the formation of cross
links in the collagen
It gives strength to the fibres.
This process is necessary for the normal production of collagen and
intercellular cement substance of capillaries.
Tryptophan metabolism
Ascorbic acid is necessary for the hydroxylation reaction during tryptophan
metabolism
Tyrosine metabolism
Vitamin C helps in the oxidation reaction during metabolism of tyrosine
Iron metabolism
ascorbic acid convert ferric iron to ferrous iron.
So, it increase the iron absorption from the intestine
Hemoglobin metabolism
It is useful for re-conversion of met-hemoglobin to hemoglobin.
Folic acid metabolism
Ascorbic acid is helping the enzyme folate reductase to reduce folic acid to
tetrahydrofolic acid
Steroid synthesis
vitamin C has role in steroid hormone synthesis.
Vitamin C helps in the synthesis of bile acids from cholesterol.
Phagocytosis
Ascorbic acid stimulates phagocytic action of leukocytes
and helps in the formation of antibodies.
Anti-oxidant property
As an anti-oxidant it may prevent cancer formation.
Cataract
Regular intake of ascorbic acid reduces the risk of cataract formation.
Deficiency Manifestations of Vitamin C
Scurvy
Deficiency of vitamin C results in scurvy.
Hemorrhagic tendency
In ascorbic acid deficiency, collagen is abnormal and the intercellular
cement substance is brittle
So capillaries are fragile, leading to increase chances of bleeding.
Internal hemorrhage
In severe cases, hemorrhage may occur in the conjunctiva and retina.
Internal bleeding may be seen as epistaxis, hematuria or melena.
Oral cavity
the gum becomes painful, swollen and spongy
Wound healing may be delayed.
Bones
bone is weak and fractures easily.
Anemia
In vitamin C deficiency anemia is seen due to reduced absorption of iron and
abnormal hemoglobin.
0 Comments