Inulin

2.1.4 Inulin

It is found to bear a close resemblance to starch except that it is a levulan rather than a dextran. The following characteristic features make it altogether different from starch, namely:

* Gives yellow colouration by iodine.

* Does not gelatinize with water.

* Not commonly found in plants in the form of granules having concentric layers, and

* Upon hydrolysis in acidic medium yields fructoses.

Synonyms Dahlin; Alantin; Alant starch.

Biological Source It occurs in certain plants of the Compositae family, such as:

Inula helenium Linn. : Roots contain inulin;

Eupatorium cannabinum Linn. : Plant contains inulin;

Cynara scolymus Linn. : Flower heads contain inulin;

Carpesium cernuum Linn. : Roots contain inulin;

Calendula officinalis Linn. : Roots contain inulin;

Aretium lappa Linn. : Roots contain 45% inulin.

Geographical Source

A. lappa – Western Himalayas from Kashmir to Simla;

C. officinalis – India, Pakistan;

C. cernuum – Temperate Himalayas and Nilgiri Hills (India);

S. scolymus – Throughout India; E. canabinum—Temperate Himalayas;

I. helenium – Europe and Asia.

Preparation Isolated from dahlia tubers and from other members of the family Compositae.

Description The crystals are spherical in shape when prepared from water.

Chemical Constituents

[Structure of INULIN showing arrangement of Fructofuranose residues in chain]

Inulin is quickly hydrolyzed by acids to D-fructose by the enzymes inulase but does not undergo hydrolysis by the amylases. However, methylated inulin upon hydrolysis gives rise to 3,4,6-trimethylfructose as a major product and 1,3,4,6- tertamethylfructose as a minor product, thereby suggesting that the fructose residues are present in the furanose form and the adjacent units are joined through C-1 and C-2 (i.e., the glycosidic hydroxyl moiety).

Uses

1. It is used in culture media as a fermentative identifying agent for certain bacterial species.

2. It is filtered exclusively by the glomeruli and is neither secreted nor reabsorbed by the tubules. Hence, it is employed as a diagnostic agent for evaluation of glomerular filteration i.e., renal–function test (or kidney function test).

3. It is considered to be valuable in the diet of the diabetic patients.

Source: Pharmacognosy And Pharmacobiotechnology By Ashutosh Kar