carbohydrates

• Awareness of the importance of carbohydrates in living systems and medicine is growing due to the increasing understanding of their biological and pharmacological relevance
• Carbohydrates are ubiquitous and perform a wide array of biological roles
• Carbohydrate-based or -modified therapeutics are used extensively in cardiovascular and hematological treatments ranging from inflammatory diseases and anti-thrombotic treatments to wound healing
• Carbohydrates


  Compounds that are essentially the hydrates of carbon, comprising carbon, hydrogen and oxygen with the last two elements existing in the same proportions as in water (H2O - 2:1)
• Compounds with same proportions as in water but are not hydrates of carbon

  • Formaldehyde [HCHO]
  • Acetic Acid [CH3COOH]
  • Lactic Acid [C3H6O3]
• Carbohydrates that do not abide in the "rule of H2O"

  • Cymarose C7H14O4
  • Digitoxose C6H12O4
  • Rhamnose C6H12O5
  • Sarmentose C7H14O4
  • Oleandrose C7H14O4
  • Digitalose C7H14O5
• Carbohydrates represent not only the sugars but also those substances that are related to them basically in structure and other characteristic features
• Carbohydrates belong to the chemical class of the aldehydes, ketone alcohols, and also the condensation polymers of these partially oxidized polyalcohol collectively known as 'Polysaccharides' or 'Oligosaccharides'
• Solubility of carbohydrates


  • With increasing complexity of the chemical structure, the water solubility decreases. Monosaccharides and disaccharides are soluble in water while polysaccharides are insoluble, hence, heat is required to dissolve them.
• Shape of carbohydrates


  • Monosaccharides and disaccharides (like sucrose) appear as white crystalline while polysaccharides (like starch) are amorphous
• Taste of carbohydrates


  • With increasing complexity of the chemical structure, the level of sweetness decreases. Monosaccharides and disaccharides taste sweet while polysaccharides taste bland.
• Hydrolysis of starch


  Starch hydrolyzes to amylodextrin → erythrodextrin → achrodextrin → maltose → 2 glucose
• Reducing sugars


  Can reduce cupric ion from Fehling's solution to produce cuprous ion
• Osazones


  Carbohydrates can form them with phenylhydrazine
• Fermentation of carbohydrates


  1. Initiated by yeast (Saccharomyces cerevisiae)

  2. Fruits and flowers are made into wine

  3. Honey is made into mead (alcoholic beverage)

  4. Malted barley is made into beer

  5. Apple is made into cider (alcoholic beverage made from the fermented juice)

  6. Molasses is made into rhum (distilled from fermented molasses)
• Oxidation of sugars


  Produces sugar acids, e.g. glucose to gluconic acid
• Reduction of sugars


  Produces sugar alcohols, e.g. mannose to mannitol
• Photosynthesis


  nCO2 + n H2O + Light Energy → (CH2O)n Carbohydrate + nO2
• Biosynthesis of sucrose


  1. Fructose 6-phosphate is converted to glucose 1-phosphate

  2. Glucose 1-phosphate reacts with UTP uridylyltransferase to form UDP-glucose Uridine diphosphate glucose

  3. UDP-glucose reacts with fructose 6-phosphate to form sucrose phosphate then sucrose

  4. UDP-glucose reacts with fructose to form sucrose directly

  5. Sucrose may remain as sucrose or be utilized to form monosaccharides then oligosaccharides or polysaccharides
• Dextrose (aka α-D-glucopyranose, D-glucose)


  Biological source: Grapes, Starch. Uses: Nutrient, ingredient in various injectable and oral formulations
• Dextrose excipient (aka Dextrose monohydrate, dextrates)


  Biological source/source: Starch. Uses: Sweetening agent, tablet binder, coating agent, replacement for liquid glucose as pharmaceutic aid
• Liquid glucose


  Biological source/source: starch. Description: Colorless/yellowish, thick, syrupy liquid; nearly odorless; sweet. Chemical constituents: Dextrose, dextrins, maltose, water. Uses: Agent of pharmaceutic necessity
• Calcium gluconate


  Biological source/source: from Gluconic acid. Description: Soluble in cold water; less irritating for parenteral use than calcium chloride. Uses: Electrolyte replenisher
• Calcium gluceptate and calcium levulinate

  Biological source/source: Calcium gluceptate: glucose, Calcium levulinate: starch and cane sugar. Description: Salts are calcemic. Uses: Electrolyte replenisher
• Ferrous gluconate


  Biological source/source: Gluconic acid. Uses: Hematinic to increase the amount of hemoglobin in the blood
• Fructose (aka D-fructose, levulose, β-D (-)-fructopyranose, β-D (-) – fructofuranose, fruit sugar)


  Biological source/source: Inversion of sucrose; honey; hydrolysis of inulin; enzymatically prepared high fructose syrup inverted sugar glucose and fructose. Description: Ketone sugar, colorless crystals or white crystalline or granular, odorless powder that has sweet taste, freely soluble in water, half as sweet to the taste as glucose. Uses: Food for diabetic patients, infant feeding formulas, intravenously, fluid, nutrient and electrolyte replenisher
• High-fructose sweetener


  Biological source/source: prepared by controlled enzymatic isomerization of Glucose (derived from starch)
• Xylose (aka D-Xylose, wood sugar)

  Biological source/source: Corn cobs, straw. Description: Sweet taste; absorbed from the small intestine; not metabolized by mammalian enzymes. Uses: Diagnostic agent for the evaluation of intestinal absorption
• Sucrose (aka Saccharum, sugar)


  Biological source: Sugarcane: Saccharum officinarum Linne (Gramineae), Sugar beet: Beta vulgaris Linne (Chenopodiaceae), Sugar maple: Acer saccharum (Aceraceae). Residual dark-colored syrup is called molasses (Use: animal food and production of ethyl alcohol)
• Fructose sweetener


  Prepared by controlled enzymatic isomerization of Glucose (derived from starch)
• Xylose (aka D-Xylose, wood sugar)


  • Sweet taste; absorbed from the small intestine
  • Not metabolized by mammalian enzymes (to significant extent)
• Biological Source/Source of Sucrose

  • Sugarcane: Saccharum officinarum Linne (Gramineae)
  • Sugar beet: Beta vulgaris Linne (Chenopodiaceae)
  • Sugar maple: Acer saccharum (Aceraceae)
• Molasses


  Residual dark-colored syrup (Use: animal food and production of ethyl alcohol)
• Lactose (aka Milk sugar)


  • Cow's milk (80-90 % water; 3% casein; 5% lactose; 0.1 to 1 % mineral slats; 2.5 to 5 % fat (butter); vitamins)
  • Odorless, faintly sweet taste
  • Stable in air; readily absorbs odor
  • Hydrolysis: yields D-glucose and D-galactose
  • Reduces Fehling's solution; undergoes mutarotation; forms osazone change in the optical rotation
  • Hydrolyzed by lactase
  • Undergoes lactic and butyric acid fermentation
• Lactulose


  • Semisynthetic sugar
  • Yields fructose and galactose upon hydrolysis
  • Poorly absorbed; remains unchanged in the colon
• Certain pharmaceutic products, such as ethanol and citric acid, are produced by the cellular respiration of carbohydrates, especially glucose.
• Embden-Meyerhof pathway


  Anaerobic conversion of glucose to pyruvic acid by glycolysis. In the absence of air, pyruvic acid may be converted to lactic acid or to ethanol. Lactic acid can be converted to energy without oxygen. Accumulation of it in the blood results to muscle cramps
• Oxidative decarboxylation of pyruvic acid

  Pyruvic acid undergoes oxidative decarboxylation to yield acetyl coenzyme A (acetyl-CoA or active acetate) which can be utilized in a variety of reactions including the acetylation of aromatic amines and alkaloids or the biosynthesis of fatty acids or steroids.
• Tricarboxylic acid cycle


  Most of the acetyl-CoA undergoes condensation with oxaloacetate to form citrate, thereby entering the TCA cycle where it is oxidized to CO2 and water with the liberation of energy
• Pentose Phosphate Pathway


  1. Oxidative phase: G6P is oxidized and decarboxylated to ribulose-5-Phosphate; products: 2 equivalents NADPH

  2. Regenerative "sugar-shuffle" phase: Conversion of ribulose-5-phosphate to G-6-Phosphate