Carbohydrates Lecture Notes PDF

Carbohydrates Presented by: Marwa Saeed Galaa Goda Department of Pharmacognosy, Faculty of Pharmacy, SCU  Objectives Definition Classification Biological importance Pharmaceutical dosage forms  C...

Carbohydrates Presented by: Marwa Saeed Galaa Goda Department of Pharmacognosy, Faculty of Pharmacy, SCU  Objectives Definition Classification Biological importance Pharmaceutical dosage forms  Carbohydrates I. Definition Carbo-hydrates means hydrates of carbon with chemical formula of Cx(H2O)y. Polyhydroxy aldehydes or ketones, or substances that hydrolyze to yield polyhydroxy aldehydes or ketones. C They are also called saccharides, which means sugars. O H  Carbohydrates II. Classification Carbohydrates Monosacchaides Oligosaccharides Polysaccharides [1 sugar unit] [2-10 sugar units] [>10 sugar units]  Carbohydrates II. Classification 1. Monosaccharides Carbohydrates that cannot be hydrolyzed into simpler carbohydrates are called as monosaccharides (CnH2nOn). Monosaccharides are further classified based on 1. Functional group: the carbonyl group of either an aldehyde (aldoses) or a ketone (ketoses), or 2. Number of carbon atoms present in their structure: triose, tetrose, pentose, hexose, etc.  Carbohydrates II. Classification 1. Monosaccharides No. of carbon Generic atoms name Aldose Ketose Aldotetrose Ketotetrose 4 Tetrose e.g., Erythrose e.g., Erythrulose Aldopentoses Ketopentoses 5 Pentose e.g., Arabinose, Xylose, Ribose e.g., Xylulose, Ribulose Aldohexose Ketohexose 6 Hexose e.g., Glucose, Galactose, Mannose e.g., Fructose  Carbohydrates 1. Monosaccharides: Aldoses  Carbohydrates 1. Monosaccharides: Aldoses -D-Ribose found in all plant and animal cells e.g., ribonucleic acid (RNA). -D-Xylose (wood sugar) prepared from bran, straw (or any woody material) by acid hydrolysis. -L-Arabinose (pectin sugar) found in gums, pectic substances.  Carbohydrates 1. Monosaccharides: Ketoses  Carbohydrates 1. Monosaccharides: Deoxysugars Deoxy sugars formed by removal of oxygen atoms from either carbon 2 [2-deoxy pentose] or 6 [6-deoxy hexose] , or both carbons 2 and 6 to produce [2,6-dideoxy hexose]. A. 2-deoxy-pentoses: Deoxy-D-ribose in the nucleic acids of all animal and plant cells (DNA). B. 6-deoxy-hexoses: 1. L-Rhamnose 2. D-Digitalose found in Digitalis glycosides C. 2,6-deoxy-hexoses: 1. Digitoxose: It is the sugar part of the Digitalis glycosides. ‘Dideoxy hexose’ 2. Cymarose: It is found in cymarin (Strophanthus glycoside)  Carbohydrates 1. Monosaccharides: Biologically important hexoses Glucose / blood sugar / grape sugar: Fructose / fruit sugar / levulose: IV injection, Diuretic food for diabetic (no need for insulin) & for infant feeding formula  Carbohydrates 1. Monosaccharides: Derivatives of hexoses 1- Sugar alcohols: like Sorbitol (mild laxative, oral or rectal enema) and Mannitol (osmotic diuretic as it is freely filtered through the renal tubules. However, as it is not reabsorbed, it continues to be osmotically active in the tubules). Mannitol is used for measuring renal filtration rate.  Carbohydrates 1. Monosaccharides: Derivatives of hexoses 2- Sugar acids: Gluconic acid and its salts. Ca, Mg, or ferrous gluconate is used (by IV or orally) for treatment of calcium deficiency, iron deficiency or magnesium deficiency.  Carbohydrates 1. Monosaccharides: Derivatives of hexoses 3- Ascorbic acid (vitamin C): In plants, glucose or galactose can be converted into ascorbic acid which is used as immunostimulant, antioxidant and to prevent deficiency of vitamin C (scurvy).  Carbohydrates 1. Monosaccharides: Derivatives of hexoses 4- Amino sugar (glucosamine): It is derived from monosaccharides by replacement of a hydroxyl group by an amino group prepared by strong acid hydrolysis of chitin. Glucosamine sulphate is used for regeneration of cartilage in joint injuries and arthritis.  Carbohydrates II. Classification Carbohydrates Monosacchaides Polysaccharides Oligosaccharides [1 sugar unit] [>10 sugar units] [2-10 sugar units]  Carbohydrates II. Classification 2. Oligosaccharides Oligosaccharides are soluble in water and hydrolysable by acids or specific enzymes. Even though they are soluble in water, they are too large to pass through the cell membrane. They are subclassified into di-, tri- and tetrasaccharides, etc. according to the number of molecules of simple sugars they yield on hydrolysis. The monosaccharide units are linked through glycosidic linkages.  Carbohydrates II. Classification 2. Oligosaccharides A. Disaccharides: On hydrolysis they yield 2 monosaccharides (similar or dissimilar). There are two types, reducing (Maltose & Lactose) or non- reducing (Sucrose). B. Trisaccharides: On hydrolysis they yield 3 monosaccharides (Raffinose). C. Tetrasaccharides: On hydrolysis they yield 4 monosaccharides (Stachyose & acarbose).  Carbohydrates II. Classification 2. Oligosaccharides: Disaccharides 5 1 1 5 5 1 2 5 5 5 1 1 Non-reducing disaccharides Reducing disaccharides  Carbohydrates II. Classification 2. Oligosaccharides: Disaccharides I. Non-reducing disaccharides: e.g., Sucrose (cane sugar), does not reduce Fehling’s solution. It has a sweetening power more than glucose and less than fructose. Uses: 1- In syrup preparation and tablet manufacture. 2- Nutrient and demulcent. 3- In high concentrations as bacteriostatic (jams). 4- In preparation of dextran (a polysaccharide used as plasma substitute).  Carbohydrates II. Classification 2. Oligosaccharides: Disaccharides I. Non-reducing disaccharides: e.g., Sucralfate a semisynthetic sucrose derivative. Aluminum sucralfate, an aluminum salt of sucrose ocatasulfate, is a medication used to treat stomach ulcers (protective barrier), gastroesophageal reflux (Al(OH)3 neutralize HCl) disease.  Carbohydrates II. Classification 2. Oligosaccharides: Disaccharides II. Reducing disaccharides: e.g., 1: Maltose (malt sugar): Maltose is prepared by partial acid hydrolysis of starch, or by using α-amylase enzyme. It has two glucose linked 1 →4. Uses: As nutrient in infant's food and in tablet manufacture.  Carbohydrates II. Classification 2. Oligosaccharides: Disaccharides II. Reducing disaccharides: e.g., 2: Lactose (or milk sugar) Lactose is the principal sugar of mammalian milk and is not present in higher plants. Lactose is obtained as a by-product during cheese manufacture. Emulsin enzyme Uses: 1- Nutrient in infant foods (Less sweet than sucrose and more easily digested). 2- Inert diluent for other drugs.  Carbohydrates II. Classification 2. Oligosaccharides: Disaccharides Lactulose Semisynthetic disaccharide prepared from lactose [galactose linked β 1→4 to fructose]. Uses: 1- laxative [It is not absorbed from gastrointestinal tract, so it is safe for diabetic patients]. 2- Hepatic encyphalopathy (it promotes uptake of ammonia by colonic bacteria as a nitrogen source for protein synthesis).  Carbohydrates II. Classification 2. Oligosaccharides B- Trisaccharides Raffinose is a non-reducing trisaccharide (glucose, fructose and galactose), known as alpha-galactosyl derivatives of sucrose. Raffinose is found in beans, broccoli, beet and soybeans. It is poorly digested in stomach and intestine, so these foods tend to cause more gas and flatulence because the raffinose is digested by bacteria once it reaches the colon.  Carbohydrates II. Classification 2. Oligosaccharides C- Tetrasaccharides Stachyose is a tetrasaccharide (glucose, fructose and 2 galactose) isolated from the tubers of Japanese artichoke and also found in soybean. Acarbose is a tetrasaccharides anti-diabetic drug used to treat type II diabetes by inhibition of alpha glucosidase, enzyme needed to digest carbohydrates. Cyclohexene amino  Carbohydrates II. Classification 2. Oligosaccharides D- Cyclodextrins: Cyclodextrins are crystalline substances obtained from partial hydrolysis of starch by the action of specific enzymes. They are composed of 5 or more α-D- glucopyranoside units linked 1-4, as in amylose. They are differentiated into : α, β and γ-cyclodextrins with 6,7 and 8 glucopyranose units, respectively.  Carbohydrates II. Classification 2. Oligosaccharides D- Cyclodextrins:  Carbohydrates II. Classification 2. Oligosaccharides D- Cyclodextrins: Uses: They are used as “drug enclosures” in order to: 1. Enhance drug solubilization (as meloxicam in Mobitil®), 2. Mask unpleasant taste (as Cetrizine in Zyrtec®), and 3. Reduce side effects (as indomethacin in Indocid®). N.B. They are arranged in cylindrical macro-rings with a hydrophobic central cavity (central core) and a hydrophilic outer surface.  Carbohydrates II. Classification Carbohydrates Monosacchaides Oligosaccharides Polysaccharides [1 sugar unit] [2-10 sugar units] [>10 sugar units]  Carbohydrates II. Classification 3. Polysaccharides Polysaccharides are large molecules containing 10 or more monosaccharide units. Carbohydrate units are connected in one continuous straight chain or branched chain. They can be differentiated according to their function into: 1. Storage polysaccharides contain only α- glucose units. Ex. starch and glycogen. 2. Structural polysaccharides contain only β- glucose units. Ex. Cellulose and chitin. Pectin is an example of structural heterosaccharides.  Carbohydrates II. Classification 3. Polysaccharides Polysaccharides are also classified into homosaccharides & heterosaccharides according to their chemistry. 1- Homosaccharides: yield on hydrolysis similar simple sugar units. Those, which yield pentose sugar are called pentosans and similarly those yielding hexose units are called hexosans. Hexosans are either glucosans [e.g., Starch, Glycogen, Cellulose, Dextran] or Fructosans [e.g., inulin].  Carbohydrates II. Classification 3. Polysaccharides Polysaccharides are also classified into homosaccharides & heterosaccharides. 2- Heterosaccharides: yield upon hydrolysis dissimilar sugar units or yield on hydrolysis monosaccharides in addition to other components such as uronic acids, sulfate esters or amino sugars [derived carbohydrates].  Carbohydrates 3. Polysaccharides A. Homosaccharides 1. Starch: α-Glucosan polysaccharide found in the seeds, fruits, tubers and roots of plants. It is composed of two polysaccharide components, Amylose (straight) & Amylopectin (branched). Uses: 1- Antidote for iodine poisoning 2- In tablet manufacture 3- Starting material for preparation of dextrins, maltose and liquid glucose.  Carbohydrates 3. Polysaccharides A. Homosaccharides 2. Glycogen: It is α-Glucosan and called animal or human starch that is stored in muscles and liver. Liver glycogen is the first line of defense against declining blood glucose levels especially between meals. 3. Cellulose: β-Glucosan forming the main constituent of cell walls of plants associated with other polysaccharides. Cellulose is an important insoluble fiber in our diet as it assists with digestive movement in the small and large intestine  Carbohydrates 3. Polysaccharides A. Homosaccharides 4. Dextran: a biopolymer of α-glucose produced by enzymes of certain bacteria (an example of biochemical conversion of a sucrose disaccharide into a polysaccharide 1 by the action of certain bacteria). 6 3 Uses 1- It is used as colloid plasma expander for emergency treatment in cases of shock due to hemorrhage, trauma or severe burns. 2- Dextran sulphates is used as anticoagulants through direct thrombin inhibition. 3- In preparation of sephadex.  Carbohydrates 3. Polysaccharides A. Homosaccharides 5. Sephadex (modified dextran): The dextran molecules are cross-linked to give a three-dimensional network of polysaccharide chains. It is water insoluble, and its beads swell in H2O. Uses: In chromatographic separation of biological compounds, as a molecular sieve. 6. Inulin: It is a linear chain fructosan. It is used in preparation of culture media and as diagnostic agent for evaluation of renal function (for measuring glomerular filtration rate).  Carbohydrates 3. Polysaccharides A. Homosaccharides 7. Chitin and Chitosan: Chitin makes up the exoskeleton of insects and shrimps, and cell walls of some fungi. It is made up of N-acetyl glucosamine containing β (1→4) glycosidic bonds, while chitosan is a deacetylated chitin product  Carbohydrates 3. Polysaccharides A. Homosaccharides 7. Chitin and Chitosan Uses: 1- Chitin is used as surgical thread that biodegrades as a wound heals. 2- Chitin & chitosan are used in cosmetics and lotions as hydrating agents. 3- As chelating agents for treating drinking water. 4- Chitosan is used to treat obesity and high cholesterol. * [Amino group (positive charge) interact with fatty acids (negative), that retard their absorption].  Carbohydrates 3. Polysaccharides B. Heterosaccharides Polymers made from more than one kind of monosaccharides or monosaccharide derivatives (uronic acid, aminosugar,..etc). Heterosaccharides can be differentiated into: 1- Polyuronides: hemicelluloses, gums, mucilages and pectic substances. 2- Mucopolysaccharides (uronic acid + amino sugar): heparin, and hyaluronic acid.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides I. Polyuronides Polyuronides contain one or more uronic acid units in their structures. They form sticky, or gelatinous solutions in water. The common uronic acids: glucuronic, galacturonic and mannuronic acids. Examples: hemicelluloses, plant gums, mucilages and pectic substances.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides I. Polyuronides 1- Hemicelluloses : accompany cellulose in the cell walls of plants 2- Plant gums: exude from plant as a result of injury or unfavorable conditions. EX. gum arabic (for kidney failure) and gum tragacanth.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides I. Polyuronides 3- Mucilage: Unlike gums, mucilage are normal products of metabolism formed within the cell (intracellular formation). EX. Plantago mucilage and seaweed mucilage.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides 3- Mucilage: I. Polyuronides Plantago mucilage Seaweed mucilage Ex. Psyllium seed Uses 1- Bulk laxative 2- Immunostimulant effect.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides 3- Mucilage: I. Polyuronides Plantago mucilage Seaweed mucilage Ex. Psyllium seed Agar, agarose & algin. Sodium alginate obtained by alkaline extraction of various species of brown algae. Agarose obtained from red algae. Uses 1- Bulk laxative 1-Sod. Alginate is antacid. 2- Immunostimulant effect. 2- Agarose is used in treatment of jaundice 3-Thickener & emulsifier in formulation of creams, ointments, jellies and tablets..  Carbohydrates 3. Polysaccharides: B. Heterosaccharides I. Polyuronides 4- Pectic substances: colloidal polyuronides of high molecular weight like pectin & protopectin. The structure of soluble pectin mainly contains arabinose and xylose and galacturonic acid group. Protopectin is the water-insoluble precursor of pectin with the aid of Protopectinase. Uses: 1- Treatment of diarrhea for neonates. 2- Detoxifying agent by conjugation with toxins.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides II. Mucopolysaccharides Mucopolysaccharides are long, unbranched heteropolysaccharide containing uronic acid & amino sugars (acetylated form of glucosamine or galactosamine). These are more commonly known as Glycosaminoglycans (Glyco/samino/glycan). Major components of connective tissue, including bone and cartilage, synovial fluid and secretions of airway mucus producing cells.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides II. Mucopolysaccharides 1- Heparin: Heparin is a highly sulfated, linear polysaccharide that is isolated from the mast cells of liver, GIT and lung. Commercially available preparations of heparin are produced from bovine lung and porcine gastrointestinal mucosa. Uses: Anticoagulant (It prevents clotting in the bloodstream through thrombin inhibition)  3. Polysaccharides: B. Heterosaccharides II. Mucopolysaccharides Enoxaparin (Clexane®) is an effective alternative to heparin. It is made from heparin by chemically breaking up the larger heparin chains into smaller fragments (low molecular weight heparin). Heparin is stronger than enoxaparin but enoxaparin is longer-lasting. Enoxaparin has an advantage over heparin because of its bioavailability. 90% of the drug is available when given in the subcutaneous form. It can also be administered in intravenous formulations.  Carbohydrates 3. Polysaccharides: B. Heterosaccharides II. Mucopolysaccharides 2- Hyaluronic acid: [sulfate free]  Carbohydrates 3. Polysaccharides: B. Heterosaccharides II. Mucopolysaccharides 2- Hyaluronic acid: [sulfate free] Present in Synovial fluid of joints, connective tissues and cartilage. It acts as lubricant and a shock absorbent in the joints. Also, it enhanced fibroblasts to synthesize collagen and elastic fibers protecting the skin from aging features and speeding up wound healing.  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides They can be differentiated according to their biological activity I. Immunostimulant Ex.1. Aloe Vera Composed of a mucilaginous polysaccharide. Aloe vera gel is used in many cosmetic products (moisturizing agent for skin or hair). Ex.2. Echinacea polysaccharides [Immulant®] Immunostimulant and antiviral polysaccharide that stimulates of phagocytic activity and uptake of foreign particles.  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides Ex.3. Schizophyllan [Schizophyllan®] a water-soluble polysaccharides elaborated by fungus Schizophyllum commune. It act as an immunostimulant and used with other antineoplastic treatments in the management of carcinomas of the lungs, stomach, uterus and breasts. Ex.4. Lentinan Immunostimulant and antineoplastic polysaccharide derived from the mycelium of shiitake mushroom body.  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides II. Hypoglycemic Ex.1. Fenugreek seed mucilage Composed of a mucilaginous polysaccharide which helps in lowering blood glucose level by slowing down digestion and absorption of carbohydrates.  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides III. Laxative Ex.1. Bran Bran is the hard outer layer of whole cereal grains such as oats, wheat, corn and rice containing protein, iron, fiber, carbohydrates, fatty acids and other nutrients. Bran is used as laxative (2 tab/day) or in weight loss program (4 tab/day).  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides IV. Anti- inflammatory Bee venom/apitoxin Apitherapy is an alternate therapy that relies on the usage of honeybee products, like honey, royal jelly and mainly bee venom or apitoxin. Bee venom/apitoxin is used for the treatment of inflammation such as rheumatism, multiple sclerosis and arthritis in addition to central nervous system diseases, such as Parkinson’s disease and Alzheimer’s disease. The venom can be introduced by manual injection or by direct bee stings.  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides IV. Anti- inflammatory Bee venom/apitoxin Bee venom contains several active molecules such as peptides, known as like melittin, apamin, and adolapin, and also enzymes, known as phospholipases and hyaluronidase. Adolapin possesses powerful anti-inflammatory and analgesic effects by blocking prostaglandin synthesis and inhibiting cyclooxygenase activity. It should be tested for its hypersensitivity before use as Melittin is the most prominent compound responsible for its allergic reactions.  Carbohydrates 3. Polysaccharides: Other biologically active polysaccharides V. Natural sweeting agents Sugars e.g., sucrose, glucose and fructose Sugar alcohols e.g., sorbitol and mannitol.