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Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

• The glycosidic linkages named according to the type of parent sugar eg.

glucosidic, galactosidic or fructosidic linkages.

• Once the glycoside is formed, the ring can no longer open up to the open-

chain form. Glycosides, therefore, are not reducing sugars.

• There are 2 types of glycosidic linkage:
O- glycosidic linkage N- glycosidic linkage

2. Reduction to Polyhydric alcohol (Alditols, see latter):

• Reducing agents are sodium amalgam (Na/Hg) or H 2-gas/Pt.

• Aldose gives an alcohol, e.g.,:

1) D-Glucose → D-Sorbitol. 2) D-Mannose → D-Mannitol.

3) D-Galactose → D-Dulcitol.

• Ketose yields an epimeric pair of alcohol, e.g.,:

D-Fructose → D-Sorbitol + D-Mannitol.

• They are sweet but slowly absorbed

• Accumulation of sorbitol and dulcitol in the tissues may cause certain

pathological conditions e.g. cataract, nephropathy

• Ribitol: Enters in the structure of Riboflavin.

• Glycerol: Present in the structure of many lipids

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