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Secondary Products
Introduction and Terpenes
Review of
Primary
Pathways
I -Glycolysis
II – Krebs Cycle
Pyruvate  Acetyl-CoA
III – Pentose
Phosphate
Pathway
Secondary Products
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What are secondary products?
Where are they found?
What do they do?
Major Types of Secondary Products
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Terpenes
Phenolics
Glycosides
Alkaloids
A few examples of secondary products
Type
Compound
Medical
Terpenes
Essential oils
Aromatherapy
Taxol - yew
Chemotherapy
Phenolics
Urushiol-poison ivy Irritant
THC - marijuana
Glycosides
Hallucinogen,
Glaucoma
Digitoxin - foxglove Heart failure
medication
Saponin - yam
Steroid source
Alkaloids
Quinine - Cinchona Anti-malarial
Cocaine - Coca
Psychoactive,
anesthetic
Terpenes (Terpenoids)
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Diverse group of lipids – about 15,000 to 30,000
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Derived from the union of 5-carbon isoprene units
(C5H8)
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Insoluble in water
Synthesized from acetyl-CoA or Glycolysis intermediates
terpenes also called isoprenes or isoprenoids
Called terpenoids if other elements included
(especially oxygen)
Isoprene Molecule
H3C
CH-CH=CH2
H2C
Two Pathways of Terpene Synthesis
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Mevalonic Acid Pathway: 3 molecules of
acetyl-CoA are joined together to form
mevalonic acid
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Mevalonic acid is a 6-carbon intermediate
Mevalonic acid is
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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
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Uses glycolysis intermediates to synthesize IPP
Isoprene Synthesis
Types of terpenes
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Classified by number of isoprene units
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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
Glandular trichomes in geranium
Trichomes
Monoterpenes: C-10
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Many monoterpenes function as insect toxins
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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
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Many essential oils are also antibacterial and
antifungal
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Some essential oils attract pollinators
Sesquiterpenes: C-15
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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
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Lactone with potent anti-malarial activity
Diterpenes: C-20
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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
Triterpenes: C-30
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Includes structurally diverse cmpds including
steroids
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Some important glycosides have a triterpene as
the aglycone – digitalis, saponins
Some mimic insect hormones and interfere
with development
Other triterpenes are antifeedants
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Azadiractin from oil in neem tree best known