glycoside

• Glycosides


  Sugar ethers; heteropolysaccharides
• Formation of glycosidic bond

  1. Hydroxyl of the sugar portion is condensed with a hydroxyl group of the non-sugar portion

  2. Bond is formed between the hydroxyl group on the first carbon atom of the sugar and a hydroxyl group on the non-sugar molecule
• Glycone


  Sugar portion
• Aglycone


  Non-sugar portion
• Glycosides


  Compounds that yield one or more sugars among the products of hydrolysis (glycosidases)
• Classification of glycosides


  • Cardiac glycoside
  • Anthraquinone glycoside
  • Saponin glycoside
  • Cyanophore glycoside
  • Isothiocyanate glycoside
  • Flavonol glycoside
  • Alcohol glycoside
  • Aldehyde glycoside
  • Lactone glycoside
  • Phenol glycoside

  
• Cardiac glycosides


  • Have specific action on the cardiac tissues
  • Increase force of Systolic contraction = ↑ heartbeat
  • Inhibit Na-K ATPase, thereby increasing Ca inside the heart muscle
  • Calcium plays a crucial role in muscle contraction, and its higher availability enhances the force of contraction in heart muscle cells
• Cardenolide


  Aglycone of cardiac glycosides

  
• Bufadienolide


  Aglycone of cardiac glycosides

  
• CPPP/Cyclopentanoperhydrophenanthrene


  Sterol nucleus essential for the binding of the cardiac glycoside to its target enzyme, Na-K ATPase

  
• Examples of cardiac glycosides

  • Digitalis
  • Convallaria
  • Apocynum
  • Adonis
  • Cactus grandifloras
  • Black hellebore
  • Strophantus
  • Squill
  • Rose bay

  
• Digitalis

  • Source: Foxglove (Digitalis purpurea)
  • Digitoxin: Very lipophilic, longer half-life (168 to 192 hrs)
  • Digoxin: More polar, shorter half-life (30 to 40 hrs)
• Convallaria

  • Source: Lily of the Valley root
  • Constituent: Convallotoxin
• Apocynum


  • Source: Black Indian Hemp/ Dogbane/ Canadian Hemp
  • Constituent: Cymarin
• Adonis

  • Source: Pheasant's eye (Adonis vernalis)
  • Constituents: Adonitoxin, Cymarin, K-strophantin
• Cactus grandifloras

  • Source: Night-blooming cereus (Selenicereus grandiflorus)
• Black hellebore


  • AKA: Christmas rose
  • Source: Rhizome and root of Helleborus niger
  • Constituent: Hellebrin
  • Green Hellebore: Cardiac depressant
• Strophantus

  • Source: Dried, ripe seed of Strophantus kombe
  • Constituent: k-strophantin
  • Strophantus gratus: contains ouabain (G-Strophantin)
• Squill


  • Source: Bulb of white variety of Urginea maritama
  • Constituent: Scillaren A
  • Effects: Expectorant, emetic, cardiotonic, diuretic
  • Red variety: Used as rat poison
• Rose bay


  • Source: Oleander/ Adelfa/ Kampanyero (Nerium oleander)
  • Constituent: Oleandrin
• Anthraquinone glycosides

  Glycosides which possess anthracene as aglycone
• Anthraquinone

  Pure anthracene derivative
• Dihydroxyphenol

  Chrysophanol & Rhein - (two hydroxyl groups)
• Trihydroxyphenol

  Emodin (three hydroxyl groups)
• Anthranol

  Reduced anthraquinones: They lack one or two oxygen atoms compared to anthraquinones
• Dianthrone

  Linking two anthraquinone units together
• Oxanthrone

  Intermediate between anthraquinone and anthranol
• Aloin type or C-glycoside

  Sugar is linked directly to the carbon atom (C-glycosidic bond) of the anthraquinone ring

  
• Cascara sagrada

  • Source: Dried bark of Rhamnus purshianus
  • Constituents: Cascarosides A and B, Cascarosides C and D
  • Addition of MgO or Alkaline earths: Reduced bitter taste
  • Casanthranol: Purified mixture of the anthranol glycosides extracted from Cascara
• Frangula


  • Source: Buckthorn bark
  • Component of Movicol® (Frangula + karaya gum → laxative, used to treat constipation
• Aloes


  • Source: Dried latex of leaves
  • Constituents: barbaloin (aloe-emodin), Chrysophanic acid
  • Use: Ingredient in compound benzoin tincture, Drastic cathartic (strong laxative), Aloe vera gel: Treatment of burns, abrasions, skin irritations
• Chinese rhubarb


  • Source: Rhizome and root of Rheum officinale, R. palmatum, R. rhaponticum
  • Constituent: Rhein anthrones
  • Used in traditional Chinese medicine for GI and renal function disorders, hyperlipidemia, cancer, and acute ischemic stroke
• Senna


  • Source: Leaflet of Alexandria senna (Cassia acutifolia) and Tinnevelly senna (Cassia angustifolia)
  • Constituent: Sennoside A and B- more potent than cascara
  • Cultivated on lands resembling rice paddies
• Chrysarobin


  • Source: Mixture of neutral principles obtained from Goa powder (Andira araroba)
  • Use: Keratolytic agent for psoriasis, trichophytosis, eczema
  • Anthralin: Replaced the use of chrysarobin
• Saponin glycosides


  Widely distributed plant glycosides comprising either steroidal or triterpene aglycones linked to carbohydrate chains
• Neutral saponin


  Steroid derivative - derived from cholesterol
• Acid saponin


  Triterpenoid derivative - derived from five carbon units (isoprene)
• Sapotoxins


  One of the most toxic plant principles; Irritating to the mucus membrane; toxic to cold blooded animals (due to their membrane-disrupting effects)
• Examples of steroidal saponin glycosides

  • Dioscorea or Yam
  • Sarsaparilla root
• Examples of triterpenoidal saponin glycosides

  • Licorice
  • Gugo
  • Tiger grass
  • Quillaja bark