Hantzsch pyridine synthesis The first major synthesis of pyridine ..


Niacin Deficiency
Nicotinamide may be toxic to the liver
at doses exceeding 3 g/day for adults
Niacin
Synthesis
Biologically
The liver can synthesize niacin from the
essential amino acid
tryptophan, requiring
60 mg of tryptophan to make one mg of niacin.

Vitamin B 6 and riboflavin are necessary for niacin synthesis from tryptophan
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The requirement for preformed niacin as a proportion of the total niacin requirement tends to be lower with higher tryptophan intakes (a greater proportion of tryptophan is available for conversion to NAD once protein synthesis needs are met) and pregnancy


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N2 - The biosynthesis of pyridine nucleotides has been examined in a number of mammalian cell lines in culture. In all lines examined, nicotinamide is incorporated by a biochemical pathway distinct from the Preiss Handler pathway for nicotinic acid. In at least the human cell line D98/AH2, there is no detectable endogenous synthesis of the pyridine ring from tryptophan. Although most cell lines examined (hamster BHK 21/13, mouse L929 and human D98/AH2) use either nicotinic acid or nicotinamide as a precursor for NAD and NADP, 2 mouse cell lines, 3T3-4E and LM ClID, are unable to utilize nicotinic acid as a source of the pyridine ring. If nicotinic acid is present in the medium, substantial amounts of intracellular desamido NAD accumulate suggesting that the last step (desamido NAD→NADP) is limiting in the Preiss Handler pathway. With nicotinamide, the only compound which accumulates in substantial amounts apart from NAD and NADP is nicotinamide ribose; there is no detectable NMN. The results of pulse labeling experiments suggest that nicotinamide ribose may be an intermediate in the nicotinamide pathway. Following growth of D98/AH2 cells in high concentrations of niacin, biosynthesis of NAD from nicotinamide was completely inhibited for at least 6 hr. The converse experiment revealed no inhibition of niacin incorporation. This observation suggests that a niacin pathway intermediate, which present evidence indicates is desamido NAD, can inhibit nicotinamide utilization. Newly synthesized NAD turns over with a half life of 2 hr in azaserine treated D98/AH2 cells. In the absence of azaserine, the nicotinamide moiety of newly synthesized NAD is lost from D98/AH2 cells to the medium with a half life of 8 hr. About 80% of the nicotinamide is lost to medium as nicotinamide ribose.


Pyridine - Synthesis & Reactions - YouTube

AB - The biosynthesis of pyridine nucleotides has been examined in a number of mammalian cell lines in culture. In all lines examined, nicotinamide is incorporated by a biochemical pathway distinct from the Preiss Handler pathway for nicotinic acid. In at least the human cell line D98/AH2, there is no detectable endogenous synthesis of the pyridine ring from tryptophan. Although most cell lines examined (hamster BHK 21/13, mouse L929 and human D98/AH2) use either nicotinic acid or nicotinamide as a precursor for NAD and NADP, 2 mouse cell lines, 3T3-4E and LM ClID, are unable to utilize nicotinic acid as a source of the pyridine ring. If nicotinic acid is present in the medium, substantial amounts of intracellular desamido NAD accumulate suggesting that the last step (desamido NAD→NADP) is limiting in the Preiss Handler pathway. With nicotinamide, the only compound which accumulates in substantial amounts apart from NAD and NADP is nicotinamide ribose; there is no detectable NMN. The results of pulse labeling experiments suggest that nicotinamide ribose may be an intermediate in the nicotinamide pathway. Following growth of D98/AH2 cells in high concentrations of niacin, biosynthesis of NAD from nicotinamide was completely inhibited for at least 6 hr. The converse experiment revealed no inhibition of niacin incorporation. This observation suggests that a niacin pathway intermediate, which present evidence indicates is desamido NAD, can inhibit nicotinamide utilization. Newly synthesized NAD turns over with a half life of 2 hr in azaserine treated D98/AH2 cells. In the absence of azaserine, the nicotinamide moiety of newly synthesized NAD is lost from D98/AH2 cells to the medium with a half life of 8 hr. About 80% of the nicotinamide is lost to medium as nicotinamide ribose.

Search results for niacin at Sigma-Aldrich

Pyridine is a toxic and soluble flammable liquid base with a distinct, strong odor. It is often considered the parent compound of several naturally occurring organic compounds. It is the preferred choice as a precursor to agrochemicals and pharmaceuticals. Initially, pyridine was extracted from coal tar or obtained as a by-product of coal gasification. The process was very expensive and inefficient as coal tar constituted only 0.1–0.2% of pyridine after extraction. Currently, pyridine and its derivatives are produced synthetically. The most commonly used reactions for pyridine synthesis are Chichibabin synthesis, Bönnemann cyclization, and Cobalt-catalyzed alkyne-nitrile cyclotrimerization, etc.