Secondary Products

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Secondary Products

• Introduction and Terpenes

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Review of Primary Pathways I -Glycolysis
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II Krebs Cycle
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Pyruvate ? Acetyl-CoA
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III Pentose Phosphate Pathway
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Secondary Products

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

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A few examples of secondary products
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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)

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Isoprene Molecule
H3C CH-CHCH2 H2C
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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

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Isoprene Synthesis
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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

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Glandular trichomes in geranium
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Trichomes
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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

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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

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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

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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