Phytochemistry 1 Monosaccharides & Oligosaccharides Lecture 3 PDF

10/10/2022 Dr. Khaled A. Nematallah 1 2 1  10/10/2022 Hexoses Item 2) D-Mannose...

10/10/2022 Dr. Khaled A. Nematallah 1 2 1  10/10/2022 Hexoses Item 2) D-Mannose 3) D-Galactose Relation to Glucose C2- Epimer C4- Epimer Constituent of polysaccharides In many glycosides and polysaccharides Occurrence (Not free) e.g. Agar and linseed mucilage From seeds of date and coffee by From agar and linseed mucilage by acid Preparation acid hydrolysis hydrolysis - Prevents urinary tract infections. - Determine liver function (Spillage of Uses - treating carbohydrate-deficient galactose in urine indicates liver glycoprotein syndrome dysfunction) 3 Hexoses Galactosemia - Genetic metabolic disorder that affects an individual ability to metabolize galactose properly. - Toxic levels of galactose-1-phosphate in various tissues. Signs and symptoms: - Lethargy, vomiting, diarrhea, failure to thrive, and jaundice. - Hepatomegaly, cirrhosis, renal failure, cataracts, brain damage, and ovarian failure. Treatment - Eliminating lactose and galactose from the diet 4 2  10/10/2022 Hexoses 4) Fructose (Levulose ,fruit sugar) - Found free in honey & fruit juices and in disaccharide sucrose or in polysaccharides e.g. inulin. - The sweetest of all natural sugars (1.73). - Colorless crystals, freely soluble in water. - It reduces Fehling’s and Barfoed’s reagents. - Forms an osazone similar to that of glucose and mannose. - Positive Rapid furfural test (Resorcinol test) for ketoses. 5 Hexoses 4) Fructose (Levulose ,fruit sugar) Preparation of Fructose Ca Fructosate (PPT) A) Large scale preparation from sucrose Acid or Enzyme Fructose + Ca(OH)2 Sucrose Glucose Hydrolysis Ca Glucosate (Solution) B) Acid hydrolysis of Inulin C) From Glucose by action of alkali 6 3  10/10/2022 Hexoses 4) Fructose (Levulose ,fruit sugar) Uses - A food for diabetics (low glycemic factor). - In infant feeding formulae (more easily digested than glucose) - Diet control 7 Deoxy sugars 2,6-Deoxy Hexose 2-Deoxy Pentose 6-Deoxy Hexose Item (Digitoxose and (2-Deoxy-D-Ribose) (α-L-Rhamnose) Cymarose) Structure Digitoxose Cymarose Part of nucleic acids In many glycosides and in Sugar parts in many cardiac Occurrence (DNA) gum acacia glycosides Aniline acetate paper test Positive with Killer Killiani’s Chemical test ----- (Yellow color) test 8 4  10/10/2022 Sugar derivatives 1) Gluconic acid and its salts - Gluconic acid is prepared from glucose by mild oxidation using either dilute HNO3 or Br2/Na2CO3 or Electrically or by fermentation using Acetobacter aceti - Gluconic acid salts are characterized by being more easily absorbed than other Ca or Fe salts. - Ferrous gluconate, (orally or by i.v.) is used in iron deficiency. - Calcium gluconate is used (by i.v. or orally) for treatment calcium deficiency 9 Sugar derivatives 2) Sorbitol - Prepared by reduction of glucose Uses: - Mild laxative. - Preparation of spans & tweens. - ISDN, ISMN—Angina (nitrated sorbitol) - In food, chewing gum and cosmetic industries (toothpaste). 10 5  10/10/2022 Sugar derivatives 3) Mannitol - Prepared by reduction of mannose Uses: - As osmotic diuretic. - As vasodilator (mannitol hexanitrate). - In laboratory diagnosis of kidney functions. (not metabolized if i.v.) 11 Sugar derivatives 4) Ascorbic acid - L-Ascorbic acid (vitamin C) is synthesized both biochemically and industrially from D-glucose. 12 6  10/10/2022 13 Oligosaccharides - Like monosaccharides, oligosaccharides are crystalline, soluble in water and have sweet taste. - They are hydrolyzed by acids or specific enzymes to yield 2-10 molecules of monosaccharides. - Most oligosaccharides crystallizes as hydrates except sucrose - The monosaccharides units are linked through glycosidic linkages. - The type of glycosidic bond is based on the orientation of the hydroxyl group at anomeric position. (α glycosidic bond or β glycosidic bond) 14 7  10/10/2022 Disaccharides 1- According to reducing properties Reducing Non-Reducing 2- According to position of linkage C1-C3 C1-C4 C1-C6 Dihexoses Dihexoses Dihexoses Turanose Gentiobiose Maltose Lactose Melibiose Cellobiose 15 A) C1-C3 Dihexoses Turanose α-D-glucopyranose - Turanose is a reducing disaccharide occurring naturally in honey. - 50% of sweetness compared to sucrose, and it has been interested as a new sweetener for sugar substitute due to low calorigenic - It has also other various functionalities such as α-glucosidase inhibitory and anti- inflammatory effects D-fructofuranose Link: α 1-3 16 8  10/10/2022 B) C1-C6 Dihexoses 1) Gentiobiose β-D-glucopyranose - Gentiobiose is a disaccharide composed of two units of D-glucose joined with a β(1-6) linkage. - Gentiobiose is incorporated into the chemical structure of crocin, the chemical compound that gives saffron its color. D-glucopyranose Link: β 1-6 17 B) C1-C6 Dihexoses 2) Melibiose - Melibiose is a reducing disaccharide formed α-D-galactopyranose by an α-1,6 linkage between galactose and glucose. - It can be formed by invertase-mediated hydrolysis of raffinose, which produces melibiose and fructose. D-glucopyranose Link: α 1-6 18 9  10/10/2022 C) C1-C4 Dihexoses 1) Maltose (Malt Sugar) - Not common in nature except in malt and germinating cereals. α-D-glucopyranose - A hydrolytic product of polysaccharides e.g. starch & dextrin. - Obtained from starch by: a) Acid hydrolysis (randomness, low yield) b) β -amylase (Yield = 80%) D-glucopyranose Link: α 1-4 19 C) C1-C4 Dihexoses 1) Maltose (Malt Sugar) Properties: - Reduces Fehling’s solution but not Barfoed’s solution. - Forms characteristic osazone → rosettes of plates. - Hydrolyzed by maltase enzyme (α-glucosidase). Uses: - A mild sweetener in foods and pharmaceuticals. - A parenteral injectable for slow release of D-glucose 20 10  10/10/2022 C) C1-C4 Dihexoses 2) Cellobiose - Not found in nature. β-D-glucopyranose - Obtained from cellulose by: - Careful acid hydrolysis - By cellulase enzyme D-glucopyranose Link: β 1-4 21 C) C1-C4 Dihexoses 3) Lactose (Milk sugar) - Naturally found in milk (Cow/goat: 4.5 - 4.8%, Human: 7.0%) - Provides 40% of the energy obtained during nursing. - To utilize lactose, it must be broken down to D-glucose and D-galactose β-D-galactopyranose D-glucopyranose Link: β 1-4 22 11  10/10/2022 C) C1-C4 Dihexoses 3) Lactose (Milk sugar) Production Cow’s milk Whey Heat or Renin Ultrafiltration Enzyme Coagulated Ion exchange Casein Concentration Curd Crystalline Lactose 23 C) C1-C4 Dihexoses 3) Lactose (Milk Sugar) Properties: - Reduces Fehling’s solution but not Barfoed’s solution. - Forms characteristic osazone → needles aggregated in clusters. - Hydrolyzed by β-glucosidases e.g. emulsin Uses: - Nutrient in infant food. - An inert diluent for other drugs 24 12  10/10/2022 Lactose intolerance - Lactose intolerance is when your body can't break down or digest lactose. - If lactose is not completely hydrolyzed and absorbed in the small intestine, it will proceed into the large intestine. - Here anerobic bacteria ferment the lactose to lactic acid and other short chain acids, in addition to CO2, H2, and methane. - This causes the symptoms of lactose intolerance 25 Lactose intolerance Symptoms: - Abdominal distention - Flatulence - Cramping - Diarrhea How to deal with: - Reduce/remove lactose by fermentation (Free lactose products) - Add lactase to food (or consume lactase) just before consuming lactose containing food 26 13  10/10/2022 27 Lactulose - Galactose-β-(1,4)-fructose - Semisynthetic sugar by alkaline rearrangement of lactose - Not absorbed in the GI tract - Used either as a laxative or in the management of portal systemic encephalopathy (PSE) (Mechanism??) - Answer: PSE is related to liver diseases, which causes problems in protein digestion and production of large amount of ammonia which cause brain toxicity. Lactulose is metabolized in distal ileum and colon by bacteria to yield lactic acid, formic acid and acetic acid which remove ammonia). 28 14  10/10/2022 Thank you 29 15