Carbohydrates (2) PDF

Carbohydrates 2 Polysaccharides I. Homo-polysaccharides: Polysaccharides containing only one type of monosaccharide units. 1- Glucosane Starch Occurrence:  Corn and other cereals; such as rice, and wheat. Chemical Composition: Starch consists of two components:...

Carbohydrates 2 Polysaccharides I. Homo-polysaccharides: Polysaccharides containing only one type of monosaccharide units. 1- Glucosane Starch Occurrence:  Corn and other cereals; such as rice, and wheat. Chemical Composition: Starch consists of two components: A- Amylose (10-20%): A linear molecule of glucose. 6 B- Amylopectin 5 4 1 4 1 (80-90%): 2 A branched 3 glucose units. Uses: 1 Tablets and powders 6 manufacture. 1 4 Antidote for iodine poisoning.  Dextrans Dextrans are water-soluble polymer of glucose. Chemical Composition: Dextrans are branched polymer of glucose  Uses and Clinical Pharmacology:  I.V. injection of dextrans is used as plasma extender (a substance that can be transfused to maintain fluid volume of the blood) for emergency in case of shock due to hemorrhage.  Cellulose  Cellulose is a linear β- 1,4-linked polymer of glucose. Source: It forms the major part of plant cell walls. Uses: - As a dietary fibers (Increases food volume without increasing caloric content, weight reduction). - Surgical dressing. - Treatment of constipation. - As an artificial tears: some derivatives are used for dry eyes, e.g. hydroxypropyl methyl cellulose (HPMC).  Fructosane Inulin  It is the reserve polysaccharide abundant in family Compositae (Inula elecampane).  It consists of linear Fructofuranose units Uses:  Inulin is not metabolized by the body and is excreted unchanged, making it a useful reagent for the testing of renal efficiency.  Used in foods & drinks industry as a source of fructose.  Inulin is not digested or absorbed in the stomach. It goes to the bowels where bacteria are able to use it to grow. It supports the growth of a special kind of bacteria (Intestinal flora) that are associated with improving bowel function and general health (Prebiotic).  II. Heteropolysaccharides: Guar gum Chemical composition:  The principal constituent of the gum is galactomannan (Polysaccharides consisting of galactose : mannose ~ 1:2).  Uses:  It can produce changes in gastric emptying and in the gastrointestinal transition time, which can delay absorption of sugars from the gut. - Regulate the rate of absorption of nutrient including sugars i.e. spreading it over a long period of time, the result is a slower rise in blood sugar level (oral hypoglycemic drug).  It lowers cholesterol levels.  Pectin Occurrence:  They are obtained commercially, from the inner portions of the peels of citrus fruits.  Also found in apple pomace (Pomace or marc is the solid remains of fruits after pressing for juice or oil). Uses: Acting as a demulcent providing a coating of the bowel. In medicine, pectin adjusts viscosity and volume of stool so that it is used against constipation (as fiber) and diarrhea.  Treatment of dysentery (an inflammatory disorder of the intestine, that results in severe diarrhea containing mucus and/or blood in the feces with fever and abdominal pain).  It has the property of conjugating toxins in the upper intestinal tract (pectin possesses a surface area composed of ultramicroscopic particles (Micelles) that have the property of colloidal absorption of toxins). Used as in combination with kaolin in many antidiarrhoeal formulations. Kapect ® (Kaolin is clay-like powder attract and hold onto bacteria).  Mucopolysaccharides They are hetero-polysaccharides of animal origin, which on hydrolysis yields amino sugar units. Chitin  It is a long-chain of a N- acetylglucosamine. It is mucopolysaccharide obtained from the shells of crabs and shrimps.  Chitin's properties and Uses: It is favorable as surgical threads, because:  It is a flexible and strong material.  It is biodegradable material, means it wears away with time as the wound heals.  Moreover, chitin has some unusual properties that accelerate healing of wounds in humans.  Chitosan  Chitosan is produced commercially by deacetylation of chitin. Uses: Chitosan is frequently sold in tablet form at health stores as a "fat binder": It is supposed to have the capability to interact with lipids and limit their absorption in the body. Therefore, chitosan can be an effective complement to help lose weight during diet period or to stabilize one's weight.  Heparin It is a mucopolysaccharide present in animal tissues. Occurrence: The main sources of commercial heparin are lung and liver tissues, pig intestine mucosa.  Chemical composition:  Because of its acidic properties, heparin is also referred to as heparinic acid.  The polymer chain contains a repeating di- saccharide units of: glucosamine N,6- disulfate and glucuronic acid 2- sulfate, linked by α,1→4 bonds. 6 6 1 1 2 2  Uses:  Heparin acts as an anticoagulant Route of administration:  Heparin is given only by I.V. or deep subcutaneous injection. (Thrombophob 60000 gel ®)  Not to be given by oral route, heparin undergoes degradation by gastric acids.  Not to be given I.M., because of the dangerous of haematoma formation. If hemorrhage occurs, the anticoagulant effects of heparin can be reversed in minutes by the administration of protamine sulfate (a strongly basic, low M.wt. protein).  As protamine SO4 is basic and positively charged it has high affinity for the acidic, negativety charged heparin inactive complex.  Chondroitin sulfate  It is normally found in cartilage around joints. It is manufactured from animal sources, such as cow cartilage.  Chemical composition:  It is a sulfated glycosaminoglycan (GAG) composed of a chain of (N-acetylgalactosamine and glucuronic acid).  Uses:  Along with glucosamine, chondroitin sulfate has become a widely used dietary supplement for treatment of osteoarthritis; Chondroitin sulfate is an important structural component of cartilage and provides much of its resistance to compression.  Hyaluronic acid It is a non-sulfated glycosaminoglycan (GAG) distributed widely in connective, epithelial and neural tissues. It is also a major component of skin, where it is involved in tissue repair. Chemical composition: It is a polymer of disaccharides, composed of (glucuronic acid and N-acetylglucosamine)  Uses:  In 1970s it was approved for use in Eye surgery i.e. corneal transplantation, cataract surgery, glaucoma surgery, ….  In 2003 the FDA approved hyaluronic acid injections for filling soft tissue defects such as facial wrinkles. It is recommended by dermatologists to improve skin texture and appearance (Youth-supporting).  Along with its use to reduce joint pain, it lubricates and protects the cartilage, acts as shock absorber.  Aminoglycoside Antibiotics  Aminoglycoside antibiotics are so named because their structure consist of amino sugars linked glycosidically.  They include Streptomycin, Kanamycin, Neomycin, Paromomycin, Tobramycin and Gentamicin. Chemical composition: The aminoglycoside antibiotics are characterized by the presences of 1,3-diaminoinositol derivative: (Inositol is cyclohexane 1,2,3,4,5,6-hexol is a with formula C6H12O6). 3 1 Streptidine 2-Deoxystreptamine Spectinamine Mechanism of action: The aminoglycosides act directly on the bacterial ribosome (Ribosome is a component of cells that assembles the twenty specific amino acids molecules to form the particular protein molecule). So; Inhibit the initiation of protein synthesis, Interfere with the translation of the genetic message. Side effects: The undesirable side effects include oto- and nephrotoxicity.  Streptomycin - Streptobiosamine (Combination of L-streptose and N- methyl L-glucosamine). - The α-hydroxy aldehyde function is a centre of instability such that streptomycin cannot be sterilized by autoclaving, but instead sterilized by ultrafiltration.  It is rarely used today as a single agent, but with other primary drugs for tuberculosis such as - Isonicotinic acid hydrazide. - Rifampin. - p-aminosalicylic acid. THANKS