Inositol: Chemistry, Absorption and Functions | Vitamins

In this article we will discuss about Inositol:- 1. Introduction to Inositol 2. Chemistry of Inositol 3. Absorption and Storage 4. Existence 5. Sources 6. Daily Requirements 7. Functions 8. Deficiency Symptoms.

Contents:

1. Introduction to Inositol
2. Chemistry of Inositol
3. Absorption and Storage of Inositol
4. Existence of Inositol
5. Sources of Inositol
6. Daily Requirements of Inositol
7. Functions of Inositol
8. Deficiency Symptoms of Inositol

---

1. Introduction to Inositol:

a. Both plant and animal tissues contain in­ositol.

b. For a good length of period the hexaphosphoric ester of inositol (phytic acid) present in cereals has been known.

c. Seven optically inactive and two optically active forms of inositol are present in na­ture of which only one inactive form has got nutritional value.

d. In 1940, Woolley et al reported that inosi­tol can prevent the development of alo­pecia in mice.

2. Chemistry of Inositol:

a. Inositol (meso-inositol or myoinositol) is hex-ahydroxycyclohexane.

The structure is given below:

b. Meso-inositol is biologically most effec­tive.

c. It is highly soluble in water.

d. It is a crystalline compound and has a sweet taste.

e. It is stable to heat in neutral acid and alka­line medium.

3. Absorption and Storage of Inositol:

Inositol is absorbed readily from the small in­testine through the portal vein and passes to the tissues through the general circulation. Excess of the requirement of this vitamin is not stored in the body but is excreted in the urine and feces or metabolised.

4. Existence of Inositol:

a. The greater part of inositol exists in bound form; although a small amount exists in the free state in muscle and other tissues.

b. It exists in the form of phospholipids in animal tissues; whereas it exists in the form of phospholipids, phytic acid and phytin in plant tissues.

c. Brain and liver contain phospholipids containing inositol. Mitochondria and microsomes also contain large amount of inositol containing phosphatides.

d. Cereals oilseeds and nuts contain large amounts of phytic acid and phytin (cal­cium or magnesium salt of phytic acid). Phytic acid (inositol-hexaphosphoric acid) is hydrolyzed by an enzyme phytase present in plants into inositol and phos­phoric acid.

Unless phytic acid is hydrolysed it is not absorbed from the intes­tines. Only a small percentage of the phytic acid present in the diet is hydrolyzed and absorbed due to the low concentration of phytase in the intestinal juice.

5. Sources of Inositol:

Yeast, meat, fruits, milk, nut, vegetables and grains contain inositol.

6. Daily Requirements of Inositol:

Not yet reported.

7. Functions of Inositol:

a. Along with cholin, inositol exerts a lipo­tropic effect.

b. Large concentration of inositol in heart muscle increases the rate of contraction.

c. Labelled inositol gives rise to labelled glucose in the body.

d. It is oxidized to glucuronic acid in the liver by oxygenase.

e. It stimulates the growth of yeast and fungi.

f. It occurs in brain tissues as phosphatidyl inositol (lipositol).

g. It causes an increase in nerve chronaxia in the rat.

h. In animals, it increases the peristalsis of the small intestines.

8. Deficiency Symptoms of Inositol:

Deficiency symptoms in mice include retarded growth, failure of lactation, alopecia (loss of hair over the body), spectacled eye (a condition due to loss of hair around the eye) and those in chicks include encephalomalacia.