Chemical and physical properties of niacin

Chemical and physical properties of niacin (vitamin B3)

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

2. April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
2

3. Essential features of the chemical
structureare:
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.
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
3

4. Chemical structures of niacin:
Nicotinic acid Nicotinamid
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
4

5. Niacin nomenclature
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
5

6. Chemical and physical properties
Nicotinic acid and nicotinamide are colorless
crystalline substances.
Each is insoluble or only sparinglysoluble in organic
solvents.
Nicotinic acid is slightlysoluble in water and
ethanol.
Nicotinamideis verysoluble in water and
moderately soluble in ethanol.
The two compounds have similar absorption spectra
in water, with an absorption maximum at ∼262 nm.
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
6

7. Chemical and physical properties
•Nicotinic acid is amphoteric and forms
salts withacids as well as bases.
•Its carboxyl group can formesters and
anhydrides and can be reduced.
•Both nicotinic acid and nicotinamide are
very stable in dryform, but in solution
nicotinamide is hydrolyzed byacids and
bases to yield nicotinic acid.
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
7

8. Chemical and physical properties
•The coenzyme forms of niacin are the
pyridinenucleotides:NAD(H) and NADP(H).
•In each of thesecompounds, the electron-
withdrawing effect of theN-1 atom and the
amide group of the oxidized pyridine nucleus
enables the pyridine C-4 atom to reactwith
many nucleophilic agents: sulfite, cyanide
and hydride ions.
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
8

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 involvesthe transfer of two electrons
in a single step.
•Thehydride transfer of nonenzymaticreactions of
the pyridine nucleotides, plus those catalyzed by
the pyridine nucleotide-dependent
dehydrogenases, is stereospecific with respect to
both coenzyme and substrate.
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
9

10. Niacin antagonists
Substituted pyridines:
•pyridine-3-sulfonic acid
•3-acetylpyridine
•isonicotinic acid hydrazine
•6-aminonicotinamide
April 16, 2018
Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
10

11. Literature
•Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
April 16, 2018 11