Vitamin b3, NIACIN

1. WATER SOLUBLE VITAMINS
(B Complex group)
NIACIN
BY : AKASH M
ROLL NO :10

2. objectives
Chemistry of Niacin
Co-enzyme form of Niacin
Niacin related diseases
Sources of Niacin
Other general information

3. Chemistry of Niacin
 Niacin is a water soluble
(B complex Vitamin) also
called as Nicotinic acid.
 It acts as co-enzyme in the
cell
 NAD+ (nicotinamide
dinucleotide) is the active
form of the vitamin.
 Its chemical name is :
Pyridine -3-carboxylic
acid.

4. Co-enzyme form of
Niacin
 NAD+ : Nicotin amide adenine dinucleotide
 NADP+ : Nicotinamide adenine dinucleotide
phosphate
i. Niacin is attached to a Ribose phosphate to
form mono nucleotide.
ii. Then it is attached to Adenosine
Monophosphate(AMP) to form
dinucleotide. This is the active form of co
enzyme.
 NAD+ & NADPH are used as co enzyme in
Reductive Biosynthetic reactions.

5. Diseases related to
Niacin deficiency
 PELLAGRA: it is caused by the deficiency of
tryptophan as well as Niacin. It is mostly observed
more in women because tryptophan metabolism is
inhibited by estrogen metabolites. The symptoms of
pellagra are as follows:-
a. Dermatitis : in early stages , bright red
erythema(superficial reddening of the skin) occurs ,
especially in the feet , ankles and face. Increased
pigmentation around the neck is called Casal’s
necklace.
b. Diarrhea : may be mild or severe with blood and
mucus. It can even lead to weight loss. Sometimes
nausea is also experienced.
c. Dementia : It is frequently seen in chronic cases. It is
a disorder of the mental processes which leads to
memory disorders , personality changes and impaired
reasoning .

7. Causes for Niacin
deficiency
 Dietary deficiency of tryptophan : Pellagra is seen among
people whose staple diet is maize. The niacin in maize is
in a bound form and is made unavailable to the body.
Tyrptophan deficiency leads to pellagra like symptoms.
 Isoniazid(INH): it is an anti-tuberculous drug, which
inhibits pyridoxal phosphate formation. Hence there is
block in conversion of tryptophan to NAD+.
 Hartnup’s disease: Tryptophan absorption from intestine
is defective in this congenital disease. And even there is
excess tryptophan excretion through urine. This lack of
tryptophan leads to deficiency of nicotinamide.
 Carcinoid syndrome : the tumor utilizes major portion of
available tryptophan for synthesis of serotonin; so,
tryptophan is unavailable.

9. Dietary sources of Niacin :The richest natural sources of
niacin are dried yeast , rice polishing , liver ,peanut , whole
cereals , legumes , meat and fish. 60 mg of tryptophan will
yield 1 mg of niacin. Almost half of body’s requirement is met
by conversion of tryptophan to niacin.
Recommended Daily Allowance(RDA) : normal requirement
is 20mg/day . During lactation additional 5mg is required.
Toxicity of Niacin : Nicotinic acid when given orally leads to
histamine release which is accompanies by itching &burning.
More than 50mg/day consumption leads to liver damage.