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Vitamin B3 Niacin
The document provides an in-depth overview of vitamin B3 (niacin), covering its various names, properties, chemical structure, dietary sources, and its role as a coenzyme in numerous metabolic reactions. It outlines the physiological functions of niacin, its recommended daily allowance, and the consequences of deficiency, such as pellagra characterized by dermatitis, diarrhea, and dementia. Additionally, it addresses potential toxicity symptoms associated with excessive niacin intake.
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Introduction to the presenter and the topic of Vitamin B3, highlighting the exploration of life in biochemistry.
Study objectives for Vitamin B3 include names, discovery, properties, occurrence, RDA, functions, digestion & absorption, metabolism, assessment, deficiency, and toxicity.
Vitamin B3 is known by various names including Niacin, Niacinamide, Vitamin P, and others related to its biochemical properties.
Niacin described as a white crystalline substance, soluble in water, stable in air, with significant characteristics.
Niacin structure explained as a pyridine derivative with its plant (nicotinic acid) and animal (nicotinamide) forms clarified.
Niacin's biochemical role as a coenzyme (NAD+/NADP+) synthesized from tryptophan and the conversion process outlined.
Niacin sources include yeast, liver, poultry, and whole grains. Tryptophan-rich foods also help in Niacin production.
RDA for adults and children specified. One Niacin Equivalent equals 1 mg Niacin or 60 mg Tryptophan.
Niacin coenzymes are crucial for oxidation-reduction reactions across various metabolic pathways generating ATP.
Niacin's coenzyme form is absorbed in the small intestine, with processes for releasing it from food sources.
Describes how Vitamin B3 converts to coenzymes in cells, with no storage and excess metabolites excreted.
Assessment involves urinary excretion of niacin metabolites to determine bodily levels.
Pellagra characterized by the '3 Ds': Dermatitis, Dementia, Diarrhea, with severe consequences if untreated.
Symptoms of Niacin toxicity include painful flush, hives, rash, excessive sweating, and potential liver damage.
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Vitamin B3 Niacin
- 1. GUL MUNEER S/O ABDUL RAZZAQUE BIOCHEMISTRY BSPART II UNIVERSITY OF SINDH 2K10/BCH/23 PROUD TO BE BIOCHEMIST WE EXPLORE THE SECRETS OF LIFE 1
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- 3. STUDY OBJECTS Names of vitamin Discovery Properties Structure Chemistry Occurrence RDA Biochemical functions Digestion & absorption Metabolism Assessment Deficiency Toxicity 3
- 4. NAMES 0F VITAMINB3 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. PROPERTIES Niacin is awhite 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. STRUCTURE Niacin (C6H5O2N) issimplest of all the known vitamins. It is pyridine derivative. O C N O OH C NH2 N 7
- 8. Nicotinic Acid (Plant form) Nicotinamide(animal form) (reduced form) 8
- 9. CHEMISTRY Precursor : Dietarytryptophan 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. The conversion oftryptophan 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. Dietary nicotinamide, niacinand 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. adenine If Phosphate here-> NADP Nicotinamide Adenine Dinucleotide 12
- 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
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- 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 Copyright 2005 WadsworthGroup, a division of Thomson Learning
- 17. BIOCHEMICAL FUNCTIONS The coenzymesNAD⁺ 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. Pyruvate + CoA+ NAD+ ------> CO2 + acetyl-CoA + NADH + H+ 18
- 19. Functions of Niacin NADand 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. Digestion and Absorptionof 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. Metabolism of B-3 Conversionof free vitamin to coenzyme in all cells No storage Excesses metabolized in liver to variety of chemicals Metabolites excreted in urine 21
- 22. Assessment of B3Status 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 23
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- 26. Dermatitis ofskin 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. Niacin Toxicity symptoms Painful flush,hives, and rash (“niacin flush”) Excessive sweating Blurred vision Liver damage, impaired glucose tolerance 27
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