A. History: Choline is an essential component of the diet of animals and is, therefore, usually included among the vitamins. Best, for the first time, pointed out the role of choline in nutrition. He also showed that choline prevented the development of fatty livers in depancreatized dogs.
B. Occurrence: Choline is widely distributed. Therichest source is egg yolk. Liver, kidney, meats, cereals and many vegetables such as beans and peanuts are other good sources. It is an important constituent of lecithins.
C. Structure: Choline (C5H15O2N) is a quaternary ammonium
compound, where out of the 4 H atoms, one is replaced by hydroxy ethyl group and the other three by 3 methyl groups
compound, where out of the 4 H atoms, one is replaced by hydroxy ethyl group and the other three by 3 methyl groupsD. Properties: Choline is water soluble and has very strong basic properties.
E. Metabolism: Choline can be synthesized in the body by methylation of ethanolamine and, therefore, strictly speaking, this is not a vitamin.
Choline may function in many ways :E. Metabolism: Choline can be synthesized in the body by methylation of ethanolamine and, therefore, strictly speaking, this is not a vitamin.
(a) It is an important constituent of phospholipids like lecithin.
(b) It undergoes esterification with acetyl-CoA to form acetyl-choline. This is an endergonic
reaction, the energy being derived from ATP. Acetylcholine is responsible for the transmission of nerve impulses in the central nervous system (CNS).
(c) It acts as an important methyl group donor in intermediary metabolism.
(d) It is an important lipotropic agent and participates in the mobilization of fat from the liver. Its absence, henceforth, causes accumulation of fat in the hepatic tissues. Using mutants of Neurospora, Horowitz has shown that the inability of the fungus to synthesize choline is due to a deficiency in the formation of an intermediate compound, N-monomethyl aminoethanol. The synthesis involves the following steps :
F. Deficiency: In the deficiency of choline, puppies develop anorexia, hens do not lays eggs and mice do not lactate normally. A low-choline diet also develops hemorrhages of the kidneys and eyes, in addition to fatty livers, in young rats. No definite symptoms of choline deficiency have been established in man. However, alcoholic cirrhosis of the liver in man is largely a result of dietary deficiency of many lipotropic agents, of which choline is an important example.
G. Human requirements: In the case of choline, the dietary requirement for human beings(d) It is an important lipotropic agent and participates in the mobilization of fat from the liver. Its absence, henceforth, causes accumulation of fat in the hepatic tissues. Using mutants of Neurospora, Horowitz has shown that the inability of the fungus to synthesize choline is due to a deficiency in the formation of an intermediate compound, N-monomethyl aminoethanol. The synthesis involves the following steps :
F. Deficiency: In the deficiency of choline, puppies develop anorexia, hens do not lays eggs and mice do not lactate normally. A low-choline diet also develops hemorrhages of the kidneys and eyes, in addition to fatty livers, in young rats. No definite symptoms of choline deficiency have been established in man. However, alcoholic cirrhosis of the liver in man is largely a result of dietary deficiency of many lipotropic agents, of which choline is an important example.has not been established.
INOSITOL
A. History: Woolley (1940) discovered that the mice,
when fed on a synthetic diet containing
all the known vitamins even, failed to grow and their hair growth was arrested. The addition of pantothenic acid, the absence of which may also cause hair changes, however, proved futile. Neither biotin nor p-aminobenzoic acid could also cure them. The curative effects were, however, obtained by the addition of phytin (obtained from cereal grain) or inositol (isolated from liver). Thus, it was
established as a vitamin of B group. This is also called as mouse antialopecia factor.
B. Occurrence: Inositol is found in muscles (hence, its nomenclature as muscle sugar),
liver, kidneys, brain, erythrocytes and tissues of the eye. Among plants, it occurs in furits, vegetables, whole grains and nuts. Milk and yeast contain appreciable quantities. Inositol is found in nature in at least 4 forms : free inositol, phytin, phosphatidylinositol and a nondialyzable complex. Inositol containing phosphatide or phosphoinositide ( = lipositol of Woolley) has been isolated in pure form from soyabeans and is also known to be present in brain and spinal cord.
C. Structure: Inositol, C6H12O6 or betterC6H6(OH)6,
is a carbocyclic hexahydric alcohol. It has 9 possible stereoisomers, of which only one myoinositol found in muscles, is biologically active and happens to be a symmetric, optically inactive mesoform.
D. Properties: Although not a sugar, inositol is sweet in taste. This is, in fact, a common
property to many polyatomic alcohols including glycerol. Inositol is soluble in water.
E. Metabolism: Inositol as phosphoinositide helps in transport processes in cells.Inositol stimulates the growth of many microorganisms such as Saccharomyces cerevisiae and
Neurospora.
It also acts as a lipotropic agent and prevents the formation of fatty livers.
Possibly, it is an intermediate between carbohydrates and aromatic substances.
F. Deficiency: Inositol deficiency results in retarded growth and a peculiar hairlessness in
mice. Lack of inositol also causes insufficient lactation in experimental animals. Deficiency of
inositol, however, does not occur in man.
G. Human requirements: The amount of inositol needed by man is not known.
when fed on a synthetic diet containingall the known vitamins even, failed to grow and their hair growth was arrested. The addition of pantothenic acid, the absence of which may also cause hair changes, however, proved futile. Neither biotin nor p-aminobenzoic acid could also cure them. The curative effects were, however, obtained by the addition of phytin (obtained from cereal grain) or inositol (isolated from liver). Thus, it was
established as a vitamin of B group. This is also called as mouse antialopecia factor.
B. Occurrence: Inositol is found in muscles (hence, its nomenclature as muscle sugar),
liver, kidneys, brain, erythrocytes and tissues of the eye. Among plants, it occurs in furits, vegetables, whole grains and nuts. Milk and yeast contain appreciable quantities. Inositol is found in nature in at least 4 forms : free inositol, phytin, phosphatidylinositol and a nondialyzable complex. Inositol containing phosphatide or phosphoinositide ( = lipositol of Woolley) has been isolated in pure form from soyabeans and is also known to be present in brain and spinal cord.
C. Structure: Inositol, C6H12O6 or betterC6H6(OH)6,
is a carbocyclic hexahydric alcohol. It has 9 possible stereoisomers, of which only one myoinositol found in muscles, is biologically active and happens to be a symmetric, optically inactive mesoform.D. Properties: Although not a sugar, inositol is sweet in taste. This is, in fact, a common
property to many polyatomic alcohols including glycerol. Inositol is soluble in water.
E. Metabolism: Inositol as phosphoinositide helps in transport processes in cells.Inositol stimulates the growth of many microorganisms such as Saccharomyces cerevisiae and
Neurospora.
It also acts as a lipotropic agent and prevents the formation of fatty livers.
Possibly, it is an intermediate between carbohydrates and aromatic substances.
F. Deficiency: Inositol deficiency results in retarded growth and a peculiar hairlessness in
mice. Lack of inositol also causes insufficient lactation in experimental animals. Deficiency of
inositol, however, does not occur in man.
G. Human requirements: The amount of inositol needed by man is not known.
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