Secondary Products III Glycosides

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Secondary Products III Glycosides
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Glycosides

• Sugar most commonly found is glucose
• Non-sugar molecule known as the aglycone and may
  be
• amino acid derivatives
• steroids
• triterpenes

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Glycosides

• Most common types
• Saponins
• Cardiac Glycosides (Cardenolides)
• Cyanogenic Glycosides
• Anthraquinone Glycosides
• Glucosinolates (sometimes not included)
• Most glycosides function as deterrents to
  herbivores

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Saponins

• Terpene glycosides
• Steroid glycosides
• Steroid-alkaloid glycosides
• Triterpene glycosides
• Sapogenins
• Properties of saponins
• Effects of saponins on water

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Useful saponins

• Saponins from yam - Disocorea spp. are the source
  of steroids used for human hormones
• Birth control pills - most synthetic but some
  still use natural hormones
• Anti-inflammatory steroids
• Licorice - Glycyrrhiza glabra produces saponins
  that possibly help gastric ulcers because they
  suppress prostoglandins

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Cardiac glycosides

• Properties
• Distribution
• Best known are digitoxin and digoxin from
  Digitalis purpurea (foxglove) 30 glycosides
• Other poisonous plants with cardiac glycosides
• Oleander - Nerium oleander - oleandrin
• Milkweed - Asclepias spp - asclepiadin
• Lily of the Valley - Convallaria sp.
  convallotoxin and convallarin
• Physiological Action

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Foxglove Digitalis purpurea
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Digitoxin
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Sugars in digitoxin

• 2 molecules of digitose
• 1 molecule of 1-acetyl digitose
• 1 molecule of glucose

Digitose
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Oleander
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Oleandrin
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Milkweeds
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Convallaria majalis
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Convallotoxin
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Cyanogenic glycosides

• Distribution
• Most derived from 4 amino acids (phenylalanine,
  tyrosine, valine, or isoleucine) or from
  nicotinic acid
• Cyanogenic glycosides are not toxic by themselves
• Two enzymes involved in toxicity
• b-glycosidase releases the sugars
• Hydroxynitrile lyase releases HCN
• Effects of HCN

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Electron Transport System
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Cyanogenic Glycosides

• Variability
• Cassava (Manioc esculenta) major food crop with
  cyanogenic glycosides
• Rosaceae (Rose Family) contains cyanogenic
  glycoside - amygdalin
• Amygdalin from apricot pits source of Laetrile

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Cassava
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Amygdalin
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Glucosinolates