| Niacin and niacinamide are vitamins of the Vitamin-B group having equivalent vitamin activity. Both are precursors in the synthesis of the pyridine coenzymes NAD and NADP involved in cell metabolism. |
Niacin
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Chemical name: pyridine-3-carboxylic acid
Other names: vitamin PP, vitamin B<sub>3</sub>
Chemical formula: C<sub>6</sub>H<sub>5</sub>NO<sub>2</sub>
CAS No: 59-67-6
Niacin
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Niacinamide
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Chemical name: pyridine-3-carboxylic acid amide
Other names: vitamin PP, vitamin B<sub>3</sub>
Chemical formula: C<sub>6</sub>H<sub>6</sub>N<sub>2</sub>O
CAS No: 98-92-0
Niacinamide
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| Niacin and niacinamide were found to be the pellagra-preventig substances in 1937, about 200 years after pellagra was first described as a disease. Niacin and niacinamide have been also referred to as vitamin PP. |
Biochemical Function
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Niacin and niacinamide are required by all living cells. They are essential component of two coenzymes, niacinamide adenine dinucleotide (NAD), and niacinamide adenine dinucleotide phosphate (NADP). More than 40 biochemical reactions dependent on them have been identified. The major function is removal of hydrogen from certain substrates and the transfer of hydrogen to another coenzyme. Reactions in which NAD and NADP are involved include the metabolism of carbohydrates, lipids and proteins.
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Endogenous Synthesis and Natural Occurrence
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The amino acid tryptophan is a precursor of niacin. This endogenous synthesis, comprising 13 steps, is not very efficient. Studies in man have shown that approximately 60 mg of tryptophan are required to produce 1 mg of niacin.
Niacin and niacinamide are naturally present in various foods.
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Stability
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Niacin and niacinamide are one of the most stable vitamins, virtually unaffected by light, moisture, acids, alkalis or oxidising agents.
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