1. Chemical and physical properties of niacin
Domina Petric, MD

2. B3
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

3. Essential features of the chemical structure are:
Pyridine nucleus substituted with a β-carboxylic acid or a corresponding amine.
Pyridine nitrogen must be able to undergo reversible oxidation/reduction (quaternary pyridinium ion to/from tertiary amine).
Pyridine carbons adjacent to the nuclear nitrogen atom must be open.
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

4. Chemical structures of niacin:
Nicotinic acid
Nicotinamid
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

5. Niacin nomenclature
Niacin is the generic descriptor for pyridine 3-carboxylic acid and derivatives exhibiting qualitatively the biological activity of nicotinamide.
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

6. Chemical and physical properties
Nicotinic acid and nicotinamide are colorless crystalline substances.
Each is insoluble or only sparingly soluble in organic solvents.
Nicotinic acid is slightly soluble in water and ethanol.
Nicotinamide is very soluble in water and moderately soluble in ethanol.
The two compounds have similar absorption spectra in water, with an absorption maximum at ∼262 nm.
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

7. Chemical and physical properties
Nicotinic acid is amphoteric and forms salts with acids as well as bases.
Its carboxyl group can form esters and anhydrides and can be reduced.
Both nicotinic acid and nicotinamide are very stable in dry form, but in solution nicotinamide is hydrolyzed by acids and bases to yield nicotinic acid.
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

8. Chemical and physical properties
The coenzyme forms of niacin are the pyridine nucleotides: NAD(H) and NADP(H).
In each of these compounds, the electron-withdrawing effect of the N-1 atom and the amide group of the oxidized pyridine nucleus enables the pyridine C-4 atom to react with many nucleophilic agents: sulfite, cyanide and hydride ions.
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

9. Chemical and physical properties
The reaction with hydride ions (H-) is the basis of the enzymatic hydrogen transfer by the pyridine nucleotides.
The reaction involves the transfer of two electrons in a single step.
The hydride transfer of nonenzymatic reactions of the pyridine nucleotides, plus those catalyzed by the pyridine nucleotide-dependent dehydrogenases, is stereospecific with respect to both coenzyme and substrate.
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

10. Niacin antagonists pyridine-3-sulfonic acid 3-acetylpyridine
Substituted pyridines:
pyridine-3-sulfonic acid
3-acetylpyridine
isonicotinic acid hydrazine
6-aminonicotinamide
November 21, 2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

11. Literature
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc
November 21, 2018