Vitamin B3 (Nicotinic Acid -Niacin and Nicotinamide/Nicotinic Acid Amide or Niacinamide)

 Vitamin B3

(Nicotinic Acid -Niacin and Nicotinamide/Nicotinic Acid Amide or Niacinamide)

(Pellagra-preventing factor, P.P factor of Goldberger)

Introduction

Pellagra was first described by Casal of Spain in 1735. Dr. Goldberger and his associates studied it between the years 1874 and 1929 and showed that some foods cured pellagra. In 1926 Smith and Hendrick identified that this food contains heat labile and heat-stable factors. The latter one cured pellagra. Dr. Goldberger named it as P-P factor.

Chemistry

Nicotinic acid or niacin is known now as pyridine- 3- carboxylic acid and found in cells as amide of nicotinic acid. In the body nicotinic acid is converted into the amide before it becomes active. In tissues, nicotinamide is present largely as a dinucleotide.

Properties

·        white crystalline substance

·        moderately soluble in water

·        soluble in alkali (salt formation), alcohol and glycerides

·        heat-stable, therefore not lost during cooking or canning

Distribution

Animal sources

·        Meat

·        fish

·        liver

·        milk

·        yeast

Body can synthesise this vitamin from tryptophan.

Plant sources

·        The husk of the cereals

·        green vegetables

·        peas

·        beans

·        tomatoes

·        Maize or white flour- negligible amount

Mode of action

In the living tissue it remains as a part of at least two enzyme systems

(i) NAD or DPN or Co I,

(ii) NADP or TPN or Co II.

Niacinamide in combination with two molecules each of ribose and phosphoric acid and one molecule of adenine forms NAD. The reduced form of NAD and NADP are NADH and NADPH respectively. This set of coenzymes takes part in various reactions in the body.

Functions

(1) Essential for growth.

(2) Takes essential part in metabolism and tissue oxidation.

(3) Helps in the formation of fats from carbohydrates.

(4) Prevents pellagra.

(5) It has a stimulating effect on central nervous system.

(6) In therapeutic doses, niacin produces the pronounced transient vasodilatation with flushing of the face, increase in peripheral blood flow and skin temperature.

Excretion

2-8 mg of this vitamin is excreted daily through the urine in adult.

Deficiency signs

Pellagra- The chief symptoms of this condition are the three D's-

·        Dermatitis

·        Diarrhea

·        Dementia

Dermatitis -Deficiency results in characteristic dermatitis, especially on the exposed parts of the body. The dermatitis begins with erythema resembling sun-burnt areas. Gradually these areas become reddish-brown, rough, scaly and keratotic.

Diarrhea-Gastro-intestinal disorders, polyneuritis and various forms of mental disorders are observed.

Dementia-Cerebral manifestations include headache, irritability, confusion, etc.

General effects are

·        inadequate growth for children

·        loss of weight  

·        weakness

·        anaemia

Daily requirement

12-18 mg for adult males and a little less in adult females