Page 103 - Medicinal Plants_PharmD general

Primary Metabolites
(Food Storage Products)

I. Carbohydrates

Carbohydrates contain C, H & O, the last two elements being usually
present in the same proportions as in water. Many, such as, sugars and
starches are important food reserves for the plant and food stuffs for man
and other animals of special pharmaceutical importance are starches.

1. Starch (Amylum)

Composition of the starch Granule:
The starch granule consists mainly of two or three components;

amylose, amylopectin and amylohemicellulose which are differently
distributed in the granule. It is surrounded by a thin membrane.
 Amylose: Amylose is a polysaccharide of long unbranched chain of 1,4

linked glucose residues (250-300 units) constituting about 20% of the
granules. It is soluble in water and gives clear blue colour with iodine.
It forms the inner layers of the granule.

 Amylopectin: Amylopectin is a phosphoric ester of a polysaccharide
of long branched chain of  1,4 linked glucose residues (each branch is
250-300 units). It forms the outer layers of the granule (80%). It is
insoluble in water but swells with it. It gives a bluish-black precipitate
with iodine.

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