Vitamin B3 Niacin

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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

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Vitamin B3 Niacin

  1. 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. 2. VITAMIN B3 BY GUL MUNEER 2
  3. 3. STUDY OBJECTS Names of vitamin  Discovery  Properties  Structure  Chemistry  Occurrence  RDA  Biochemical  functions  Digestion & absorption  Metabolism  Assessment  Deficiency  Toxicity 3
  4. 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)  4
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  6. 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. 6
  7. 7. STRUCTURE Niacin (C6H5O2N) is simplest of all the known vitamins. It is pyridine derivative. O C N O OH C NH2 N 7
  8. 8. Nicotinic Acid (Plant form) Nicotinamide (animal form) (reduced form) 8
  9. 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. 9
  10. 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 10
  11. 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. 11
  12. 12. adenine If Phosphate here -> NADP Nicotinamide Adenine Dinucleotide 12
  13. 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. 14. Niacin Sources 14
  15. 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. 15
  16. 16. 16 Copyright 2005 Wadsworth Group, a division of Thomson Learning
  17. 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.  17
  18. 18. Pyruvate + CoA + NAD+ ------> CO2 + acetyl-CoA + NADH + H+ 18
  19. 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 19
  20. 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  20
  21. 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  21
  22. 22. Assessment of B3 Status Urinary excretion of niacin metabolites  N-methyl nicotinamide  2-pyridone  22
  23. 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 23
  24. 24. Dermatitis of Pellagra 24
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  26. 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) 26
  27. 27. Niacin  Toxicity symptoms Painful flush, hives, and rash (“niacin flush”)  Excessive sweating  Blurred vision  Liver damage, impaired glucose tolerance  27
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