Page 47 - Pharmd general phytochemistry I-Final2024_LEUCTERS

Medicinal Glycosides

Definition:

Glycosides are non-reducing organic compounds that on hydrolysis
yield:

 A sugar part ( glycone, of one or more monosaccharide units).

 A non-sugar part ( aglycone, also called genin ).

Glycoside Sugar part (Glycone) + Non-sugar part ( Aglycone)
(Genin)

Biosynthesis

 The aglycone and the sugar parts are biosynthesized separately
and then coupled to form a glycoside.

 The coupling of the sugar and aglycone takes place in the same
way, irrespective of the structural type of the aglycone.

 Phosphorylation of a sugar yields a sugar 1-phosphate, which
reacts with a uridine triphosphate (UTP) to form a uridine
diphosphate sugar (UDP-sugar) and inorganic phosphate.

 This UDP-sugar reacts with the aglycone to form the glycoside and
a free UDP.

Sugar Phosphorylation Sugar 1-phosphate UTP UDP-sugar + PPi

Aglycone

Sugar-aglycone + UDP
(Glycoside)

Classification and Nomenclature

(1)-According to the type of the glycosidic linkage:
α- glycosides or β- glycosides : according to
weather the sugar part( glycone )is an α- or β- sugar.

α-

1 R 1

β- Genin R

1 1

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