Carbohydrates 2

• Carbohydrates are aldehydes or ketone derivatives of polyhydric alcohols containing C, H, and O in the ratio 2:1 as in H2O
• Classification of carbohydrates:

  • Sugars
  • Monosaccharides: cannot be hydrolyzed to simple sugar substances, include trioses, tetrose, pentoses (xylose, ribose, arabinose, rhamnose), and hexoses (glucose, galactose, mannose, fructose)
  • Oligosaccharides: composed of more than one saccharide group, include disaccharides (sucrose, lactose, maltose) and trisaccharides (raffinose)
  • Polysaccharides
  • Homoglycans
  • Heteroglycans
• Biosynthesis of carbohydrates involves the production of monosaccharides by photosynthesis, which consists of light reactions converting electromagnetic energy into chemical energy and enzymatic reactions fixing carbon dioxide into sugar
• Sugar and sugar-containing drugs:

  • Sucrose: sources include sugar cane, sugar beets, sugar maple; used as a pharmaceutic necessity for syrup, demulcent, and preservative
  • Dextrose: sources include grapes and hydrolysis of starch; used as a nutrient
  • Fructose: sources include sweet fruits and honey; used as food for diabetic persons
  • Lactose: sourced from fresh pasteurized or unpasteurized milk; used as a tablet diluent
  • Xylose: obtained by boiling corn cobs, straw, or similar materials with dilute acid; used as a diagnostic agent
• Drugs containing compounds metabolically related to sugars:

  • Products of glycolytic and oxidative metabolism
  • Cherry: used in the preparation of cherry juice and as a flavored vehicle
• Acids used in pharmaceuticals:

  • Citric Acid: commercially obtained from lemons, limes, or pineapple; used as an acidulant in effervescent formulations
  • Lactic Acid: used in infant feeding formulas
  • Tartaric Acid: obtained as a byproduct of the wine industry, substitute for citric acid
• Alcohol or Ethanol products:

  • Brandy: distilled wine, depressant
  • Whiskey: distillation product from fermented malted grain, depressant
  • Rum: fermented product from molasses
  • Wine: mild stimulant and tonic
• Products of reductive metabolism:

  • Sugar alcohols like dulcitol, mannitol, sorbitol
  • Mannitol: obtained by reduction of mannose or isolation from Manna, used as an osmotic diuretic
  • Sorbitol: obtained from the ripe berries of mountain ash, used in toothpaste, chewing gums, and dietetic products
• Polysaccharides and polysaccharide-containing drugs:

  • Polysaccharides are polymers of monosaccharides linked through glycosidic linkages
  • Homoglycans contain one type of monosaccharide unit, while heteroglycans contain more than one kind of monosaccharide
• Tests for Carbohydrates:

  1. Reduction of Fehling’s solutions:

  • Brick red precipitate of cuprous oxide
  • Reducing sugars include all monosaccharides and many disaccharides
  • Non-reducing sugar includes some saccharides like sucrose
• Tests for Carbohydrates:

  2. Molisch’s test:

  • General test for carbohydrates
  • Produces a purple color when treated with alpha naphthol and concentrated sulfuric acid
• Tests for Carbohydrates:

  3. Osazone formation:

  • Formed by heating a sugar solution with phenylhydrazine HCl, Na acetate, and acetic acid
  • Forms yellow insoluble compound of varying structures called osazone to identify different sugars
• Tests for Carbohydrates:

  4. Test for pentoses:

  • An equal volume of HCl acid containing a little phloroglucinol
  • Formation of red color
• Tests for Carbohydrates:

  5. Resorcinol test for ketones or Selivanoff’s test:

  • Resorcinol and concentrated HCl
  • Forms a red color
• Tests for Carbohydrates:

  6. Keller-Killiani test for deoxysugars (cardiac glycosides):

  • Sugar dissolved in acetic acid containing a trace of FeCl3 and H2SO4
  • Reddish-brown color is produced at the junctions of the liquid