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Secondary Products III Glycosides

Secondary Products III Glycosides. Glycosides. Sugar most commonly found is glucose Non-sugar molecule known as the aglycone and may be amino acid derivatives steroids triterpenes. Glycosides. Most common types Saponins Cardiac Glycosides (Cardenolides) Cyanogenic Glycosides

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Secondary Products III Glycosides

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  1. Secondary Products III Glycosides

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

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

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

  5. 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 - Glycyrrhizaglabra produces saponins that possibly help gastric ulcers because they suppress prostoglandins

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

  7. Foxglove Digitalis purpurea

  8. Digitoxin

  9. Sugars in digitoxin • 2 molecules of digitose • 1 molecule of 1-acetyl digitose • 1 molecule of glucose Digitose

  10. Oleander

  11. Oleandrin

  12. Milkweeds

  13. Convallaria majalis

  14. Convallotoxin

  15. 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

  16. Electron Transport System

  17. 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

  18. Cassava

  19. Amygdalin

  20. Glucosinolates

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