Carbohydrates and Derived Products in Pharmacognosy

Plant Exudates

• Acacia Gum:
  • Gum of choice due to its compatibility with other plant hydrocolloids and starches
  • Uses: demulcent, emulsifying agent, thickening agent, binding agent for tablets, colloidal stabilizer, and in candy and other food products
• Tragacanth:
  • Obtained from the stems and branches of Astragalus gummifer
  • Chemical constituents: Tragacanthin (30-40%) and Bassorin (60-70%)
  • Uses: demulcent in cough and cold preparations, thickening, suspending, and emulsifying agent, binding agent in tablets, stabilizer for ice cream and sauces, and reported to inhibit the growth of cancer cells
• Karaya Gum:
  • Obtained from the tree Sterculia urens
  • Uses: bulk laxative, adhesive for dental fixtures and ostomy equipment, ingredient in lozenges for sore throat, emulsifier, thickener, and stabilizer
• Ghatti Gum:
  • Also known as Indian Gum, alternative to Acacia Gum
  • Obtained from the tree bark of Anogessius latifolia
  • Uses: emulsifier, thickener, and stabilizer

Carbohydrates

• Definition: hydrates of carbon, containing Carbon, Hydrogen, and Oxygen
• Classification: Sugars and Polysaccharides
• Sugars:
  • Monosaccharides (e.g. Glucose), Disaccharides (e.g. Sucrose), and Oligosaccharides (e.g. Raffinose)
• Polysaccharides:
  • Made up of long chains of monosaccharides linked by glycosidic bonds
  • Examples: Cellulose and Starch

Monosaccharides

• Classified based on the number of carbon atoms in a molecule
• General formula: Cn H2n On
• Examples:
  • Lactose:
    • Odorless and has a faintly sweet taste
    • Broken down into D-glucose and D-galactose
    • Uses: as tablet diluent, nutrient in infant's food, and minor role in establishing intestinal microflora
  • Lactulose:
    • Semisynthetic sugar prepared by alkaline rearrangement of lactose
    • Yields fructose and galactose upon break down
    • Uses: laxative in chronic constipation, and decrease the blood ammonia concentration in portal-systemic encephalopathy
  • Xylose:
    • Also known as wood sugar, obtained from boiling corn cobs, straw, or similar materials with dilute acid
    • Uses: as a diagnostic agent to evaluate intestinal absorption, and as an osmotic diuretic
  • Sorbitol:
    • Also known as D-glucitol, obtained from the ripe berries of the mountain ash
    • Uses: ingredient in toothpaste and chewing gums, urologic irrigation, and dietetic beverages

Polysaccharides and Related Compounds

• Starch:
  • Most widely distributed organic compound in plants
  • Occurs in seeds, pith, medullary rays, cortex of stems and roots of plants
  • Generally a mixture of two structurally different polysaccharides: amylose and amylopectin
• Cellulose Derivatives:
  • Uses: surgical dressing, textiles industries, pure cellulose for the manufacture of explosives, and controls flow of percolation
  • Examples:
    • Methylcellulose: Suspending, thickening agent, and tablet excipient
    • Hydroxypropyl Methylcellulose (HPMC): Suspending agent, tablet excipient, microcrystalline cellulose, and bulk laxative
    • Microcrystalline Cellulose: Suspending agent, topical protectant, and ophthalmic solutions
    • Pyroxylin: Soluble Guncotton, used in explosives