Page 116 - Pharmd general phytochemistry I-Final2024_LEUCTERS

Source:
 Lactulose is a semisynthetic sugar prepared by alkaline rearrangement of lactose.
 It yields fructose and galactose upon hydrolysis.

Uses:
1- Used in chronic constipation in a dose of 10-20 g. Lactulose is poorly absorbed,

and most orally ingested lactulose reaches the colon unchanged. Bacteria in the
colon metabolize the disaccharide to acetic acid and lactic acid. Sufficient
accumulation of these irritating acids causes a laxative effect.
2- The most significant therapeutic use of this sugar is to decrease the blood ammonia
concentration in portal-systemic encephalopathy. The acidified stools trap
ammonia as the ammonium ion; reabsorption is thus prevented, and blood
ammonia levels may be decreased by 25 to 50%.
Doses:
 20 to 30 g of lactulose as syrup 4 times a day.

Polysaccharides

Homopolysaccharides

 Polysaccharides containing only monosaccharide units.

Starch

Occurrence:
 Although starch is widely distributed in the plant kingdom, relatively few plants

provide starch on larger scale; corn and other cereals, such as rice and wheat,
contribute to the world’s supply.

Chemical Composition:
 Starch is not a single polysaccharide, but consists of two components, amylose

and amylopectin. The percentage of amylose is depending on the source from
which the starch is obtained.
A- Amylose (10-20%)
 It is a linear molecule composed of 250-300 D-glucopyranose units uniformly linked
α-I,4 glucosidic linkage.
 It is hot water-soluble and gives with iodine a deep blue complex.

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