The term nicotinic acid comes from mcetine, a tohacco constituent, because one can isolate acid when nicotine is oxidized by vigrous chemical means.
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Such a reaction however, does not occur when smoke is inhaled. The term niacin is used as a substitute for nicotinic acid. This vitamin was reported by Elvehjem, Wooley and their associates in 1937.
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This vitamin plays important role in carbohydrate metabolism in tissues and also participates in other forms of metabolism.
It is very important for the oxidative metabolism as it forms enzymatic system like vitamins Bi and B». It also influences the activity of the degestive glands and haematopoietic organs.
Niacin has very simple structure consisting the pyridine ring with a carboxyl group in /9 position.
Niacin is a white, odourless crystalline solid with an acidic tart taste; Its melting point is 237°C.
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It is quite soluble in water and insoluble in fat-solvents. It is very stable so that it is not inactivated by air, light, heat, acids and alkalis. It is not destroyed in ordinary cooking processes.
Occurrence and availability of Nicotinic acid or niacin:
It is found in small amounts in various plants and animal tissues. Excellent sources are liver, yeast, wheat germ, lean meat, whole cereals and pulses, etc. Common fruits and vegetables contain very little of it.
Daily requirement: The recommended dietary requirement of niacin for children is from 8 to 15 mg per day and for adults, from 13 to 18 mg. For women in pregnancy and lactation, the requirement may be increased to some extent.