VITAMIN B3 GUL MUNEER Niacin Niacinamide 0R Nicotinamide Vitamin P OR PP (pellagra preventive) Pellagra preventive factor Anti black tongue factor Nicotinic acid Vitamin G (after Goldberger’s death, vitamin B3 was some times called in his honor) Structure of Vitamin B3 Function of Vitamin B3 DISCOVERY of Vitamin B3 PROPERTIES of Vitamin B3 Nicotinic Acid (Plant form) CHEMISTRY of Vitamin B3 Sources of Vitamin B3 RECOMMENDED DAILY ALLOWANCE (RDA) of Vitamin B3 BIOCHEMICAL FUNCTIONS of Vitamin B3 Digestion and Absorption of Dietary Niacin Metabolism of B-3 Deficiency of B3

1. GUL MUNEER
S/O ABDUL
RAZZAQUE
BIOCHEMISTRY
BS PART II
UNIVERSITY OF
SINDH
2K10/BCH/23
PROUD TO BE
BIOCHEMIST
WE EXPLORE THE
SECRETS OF LIFE
1

2. VITAMIN B3
BY
GUL MUNEER
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3. STUDY OBJECTS
Names of
vitamin
 Discovery
 Properties
 Structure
 Chemistry
 Occurrence
 RDA
 Biochemical

functions
 Digestion &
absorption
 Metabolism
 Assessment
 Deficiency
 Toxicity
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4. NAMES 0F VITAMIN B3
Niacin
 Niacinamide 0R Nicotinamide
 Vitamin P OR PP (pellagra
preventive)
 Pellagra preventive factor
 Anti black tongue factor
 Nicotinic acid
 Vitamin G (after Goldberger’s
death, vitamin B3 was some times
called in his honor)

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6. PROPERTIES
Niacin is a white crystalline
substance. It is soluble in water &
ethyl alcohol but is less soluble in
ether & benzene. It is stable in air &
heat. Nicotinamide, when pure,
occurs as white needle like crystals.
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7. STRUCTURE
Niacin (C6H5O2N) is simplest of
all the known vitamins. It is
pyridine derivative.
O
C
N
O
OH
C
NH2
N
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8. Nicotinic Acid (Plant
form)
Nicotinamide (animal form)
(reduced form)
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9. CHEMISTRY
Precursor : Dietary tryptophan
The coenzymes of Niacin (NAD⁺ & NADP⁺)
can be synthesized by the essential amino
acid tryptophan.
 The term “Niacin” is used for Nicotinic acid.
 The amide form of Niacin is known as
niacinamide or nicotinamide.
 The conversion of Niacin to niacinamide
takes place in the kidney, brain slices and
liver slices.
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10. The conversion of tryptophan to nicotinic
acid in the body takes place through a
series of intermediate steps, which are
represented below:
Tryptophan → Kynurenine → 3hydroxykynurenine → 3hydroxyanthranilic acid → …… →
Quinolinic acid → Nicotinic acid
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11. Dietary nicotinamide, niacin and tryptophan
contribute to the synthesis of the
coenzymes NAD⁺ and NADP⁺.
Niacin undergoes a series of reactions to
produce NAD⁺ and NADP⁺.
60mgs tryptophan=1mg of niacin for the
synthesis of coenzymes.
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12. adenine
If Phosphate here ->
NADP
Nicotinamide Adenine Dinucleotide
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13. OCCURRENCE
Yeast (most abundantly)
 Liver
 Salmon
 Red meat
 Poultry
 Vegetables & fruits (poor)
 whole grains
 Pulses & peanuts
 Note: Milk & eggs contain very little
or no Niacin, are good pellagrapreventive foods because of their
high content of Tryptophan.

13

14. Niacin
Sources
14

15. RECOMMENDED DAILY
ALLOWANCE (RDA)



Adult (men) 15-20 mg/day
Children 10-15mg/day
Adult (women) 13-15mg/day
NOTE : One Niacin Equivalent (NE) = 1 mg
Niacin or 60 mg of Tryptophan.
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Copyright 2005 Wadsworth Group, a division of Thomson Learning

17. BIOCHEMICAL FUNCTIONS
The coenzymes NAD⁺ and NADP⁺ are involved
in a variety of “oxidation-reduction reactions”.
 A large number of enzymes belonging to the
class “oxidoreductase” are dependent on NAD⁺ or
NADP⁺.
 NAD⁺ and NADP⁺ participate in almost all the
metabolisms (carbohydrate, lipid, protein etc).
 Involved in electron transport chain to generate
ATP.

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18. Pyruvate + CoA + NAD+ ------> CO2 + acetyl-CoA + NADH + H+
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19. Functions of Niacin

NAD and NADP participates in 200+ reactions in the
body. 2 NAD+
2NADH + H+
Glucose
Pyruvate
NAD+
Pyruvate
NAD+
NADH + H+
Lactate
NADH + H+
Isocitrate
NAD+
Alpha-ketogluterate
NAD+
NADH + H+
Malate

Electron transport chain
Alpha-ketogluterate
NADH + H+
Succinyl CoA
Citric Acid
Cycle
Oxaloacetate
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20. Digestion and Absorption of Dietary
Niacin
Coenzyme form in food
 hydrolysis in small intestine to free
vitamin
 absorbed in duodenum
 nicotinic acid protein bound in corn
 requires alkali treatment (lime) to
release niacin

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21. Metabolism of B-3
Conversion of free vitamin to
coenzyme in all cells
 No storage
 Excesses metabolized in liver to
variety of chemicals
 Metabolites excreted in urine

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22. Assessment of B3 Status
Urinary excretion of niacin
metabolites

N-methyl nicotinamide
 2-pyridone

22

23. Deficiency of B3
 Pellagra
 commonly
1.
referred to as 3 Ds
Dermatitis
 Inflammation
2.
Dementia
 confused,
3.
of skin
disoriented
Diarrhea
 irritation/inflammation

of mucous membranes
4th D
− if not treated may lead to Death
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24. Dermatitis of Pellagra
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26.  Dermatitis of skin
 Inflammation
Found in the areas of the skin exposed to sun
light (neck, dorsal part of feet, ankle, face).

 Diarrhea
 Increased frequency and
fluidity of the stools, often with
blood and mucus. (loose stools)
 Dementia
 Degeneration of nervous
tissue (weakness of mind)
 Symptoms include:
Anxiety (fear and worry)
Irritability (respond or
reaction to stimulus)
Poor memory
Insomnia (sleeplessness)
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27. Niacin

Toxicity symptoms
Painful flush, hives, and rash (“niacin
flush”)
 Excessive sweating
 Blurred vision
 Liver damage, impaired glucose
tolerance

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