Hydrotropy: Definition and Importance

In this article we will discuss about:- 1. Introduction to Hydrotropy 2. Definition of Hydrotropy 3. Biological Importance.

Introduction to Hydrotropy:

Moore and Parker (1901) studied the solvent action of 5% aqueous solution of bile salts on fatty acids (and their salts).

The solubility of acids in water was less than 0.1%, in bile salt solution was 0.5% and the solubility was increased to 4.0% when 1% of lecithin was added.

The fatty acids could be readily recovered from solutions by extraction with solvents showing that the fatty acid molecule had not been altered.

Neuberg (1916) suggested that substances having the power of making water-insoluble sub­stances water-soluble should be called “hydrotropic substances.”

Definition of Hydrotropy:

It is the process by which water-insoluble sub­stances are made water-soluble by hydrotropic sub­stances.

Hydrotropic substances:

Cholic acids, ben­zoic acids, hippuric acids, phenyl acetic acid, and soaps of higher fatty acids.

Water-insoluble substances:

Fats, phospho­lipids, sterols, calcium carbonate, calcium phos­phate, magnesium phosphate, and uric acid.

Biological Importance of Hydrotropy:

i. Substances so dissolved by hydrotropy are diffusible through membranes.

ii. In the body, hydrotropic substances are found not only in bile but also in intesti­nal juice, extracts of intestinal mucosa, blood plasma and places where such sub­stances are particularly useful in helping absorption and transport of insoluble sub­stances such as cholesterol and fatty acids formed by digestion.

iii. The hydrotropic substances have the power of decreasing surface tension, e.g., bile salts reduce the surface tension of fats and make emulsification for lipase action.