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Sugar derivatives
There are many important compounds that are derived from monosaccharides. They include sugar acids, sugar alcohols, deoxy sugars and amino sugars
1- Sugar acids
They are the oxidation products of monosaccharides. According to the site of oxidation sugar acids are classified into:
a- Aldonic acids
It is produced by oxidation of carbonyl group (C1 in aldoses) to carboxylic group e.g. gluconic acid from glucose.
H C O COOH H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH
CH2 OH CH2 OH Glucose Gluconic acid b- Uronic acids
It is produced by oxidation of the last carbon e.g. glucuronic acid from glucose.
H C O H C O H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH
CH2 OH COOH Glucose Glucuronic acid
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Glucunonic acid is important in:
- Detoxication reactions
- Biosynthesis of mucopolysaccharides
- Metabolism of bilirubin
- Excretion of steroids.
c- Aldaric acid (Saccharic acid)
It is a dicarboxylic acid resulting from oxidation of both carbonyl carbon and last carbon e.g. glucaric acid from glucose.
H C O COOH H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH
CH2 OH COOH Glucose Saccharic acid d- L-Ascorbic acid (vitamin C)
It is a water soluble vitamin. It is a 6-carbon sugar acid derived from glonic acid.
2- Sugar alcohols
Aldoses and Ketoses may be reduced at the carbonyl carbon to the corresponding sugar alcohols
D-Sorbitol from D-glucose
D-mannitol from D-mannose
D-ribitol from D-ribose
Inositol is a cyclic alcohol derived from glucose.
OH OH H H H H H H OH OH OH OH
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It is a member of vitamin B complex that acts as a lipotropic factor preventing accumulation of fats in the liver
Also, inositol triphosphate has a role in the mechanism of action of some hormones.
3- Deoxysugars
These are monosaccharides with one hydroxyl group (usually at C2) is replaced by hydrogen e.g. 2-deoxyribose which is a constituent of DNA.
4- Amino sugars
These are monosaccharides in which the hydroxyl group at C2 is replaced by amino group.
Glucosamine and galactosamine are examples of amino sugars.
H C O H C O
H C OH H C NH2 HO C H HO C H H C OH H C OH H C OH H C OH
CH2 OH CH2 OH Glucose Glucosamine Amino sugars are important for biosynthesis of mucopolysaccharides and glycoproteins.
Glucosamine which is derived from glucose is a constituent of heparin and hyaluronic acid
Galactosamine which is derived from galactose is a constituent of chondriotin sulphate.