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Secondary Products

Secondary Products. Introduction and Terpenes. Review of Primary Pathways I -Glycolysis. II – Krebs Cycle. Pyruvate  Acetyl-CoA. III – Pentose Phosphate Pathway. Secondary Products. What are secondary products? Where are they found? What do they do? Major Types of Secondary Products

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Secondary Products

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  1. Secondary Products Introduction and Terpenes

  2. Review of Primary Pathways I -Glycolysis

  3. II – Krebs Cycle

  4. Pyruvate  Acetyl-CoA

  5. III – Pentose Phosphate Pathway

  6. Secondary Products • What are secondary products? • Where are they found? • What do they do? • Major Types of Secondary Products • Terpenes • Phenolics • Glycosides • Alkaloids

  7. A few examples of secondary products

  8. Terpenes (Terpenoids) • Diverse group of lipids – about 15,000 to 30,000 • Insoluble in water • Synthesized from acetyl-CoA or Glycolysis intermediates • Derived from the union of 5-carbon isoprene units (C5H8) • terpenes also called isoprenes or isoprenoids • Called terpenoids if other elements included (especially oxygen)

  9. Isoprene Molecule H3C CH-CH=CH2 H2C

  10. Two Pathways of Terpene Synthesis • Mevalonic Acid Pathway: 3 molecules of acetyl-CoA are joined together to form mevalonic acid • Mevalonic acid is a 6-carbon intermediate • Mevalonic acid is • phosphorylated with two phosphate groups - pyrophosphate (P-P) • decarboxylate and dehydrated to produce isopentyl pyrophosphate (isopentyl diphosphate) - IPP • IPP the activated building block • Mevalonate-Independent Pathway • Uses glycolysis intermediates to synthesize IPP

  11. Isoprene Synthesis

  12. Types of terpenes • Classified by number of isoprene units • sometimes compounds highly modified so its difficult to pick out isoprenes • Hemiterpenes - contain 1 isoprene unit (5-C) • Monoterpenes - contain 2 isoprene units (10-C) • Sesquiterpenes - 3 isoprenes (15-C) • Diterpenes - 4 isoprenes (20-C) • Triterpenes - 6 isoprenes (30-C) • Tetraterpenes - 8 isoprenes (40-C) • Polyterpenes - over 10 isoprenes

  13. Glandular trichomes in geranium

  14. Trichomes

  15. Monoterpenes: C-10 • Many monoterpenes function as insect toxins • Pyrethrins – neurotoxins • Conifer resins – mixture of monoterpenes • Essential oils - many are insecticidal • Recent study showed that some essential oils released after the first insect attack – essential oil attracted predators to attacking insect • Many essential oils are also antibacterial and antifungal • Some essential oils attract pollinators

  16. Sesquiterpenes: C-15 • Strong feeding repellants to insects and mammals • Some antimicrobial as well • Often have a lactone ring • Gossypol in cotton responsible for insect resistance in some varieties (possible new spermicide) • Artemisinin produced by Artemesia annua • Lactone with potent anti-malarial activity

  17. Diterpenes: C-20 • Toxins and feeding deterrents • High boiling point so not volatile essential oil - referred to as resins • Some diterpenes skin irritants • Cytotoxic lactone from Podocarpus have antileukemia activity • Taxol from Taxus is antimitotic - used to treat ovarian and breast cancer

  18. Triterpenes: C-30 • Includes structurally diverse cmpds including steroids • Some important glycosides have a triterpene as the aglycone – digitalis, saponins • Some mimic insect hormones and interfere with development • Other triterpenes are antifeedants • Azadiractin from oil in neem tree best known

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