Secondary Products - II

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Secondary Products - II

• Phenolics

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Phenolics
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Synthesis of Phenolics

• Phenolics are synthesized by a number of
  different pathways
• Two most important
• Shikimic acid pathway - more important in plants
• Malonic acid pathway - more important in fungi

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Shikimic Acid Pathway

• Converts intermediates from glycolysis
  (phosphoenol-pyruvate) and the PPP
  (erythrose-4-PO4) into the aromatic amino acids
  phenylalanine, tryptophan, and tyrosine

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See Shikimic Acid Pathway
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See Pathway for Phenolic Secondary Products
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Simple Phenolics

• Allelopathic compounds
• Defense cmpds against insect herbivores and fungi
• Certain phenolics (furanocoumarins) are
  phototoxic - not toxic till activated by sunlight
  (near UV-A)
• Activated furanocoumarins can insert into DNA and
  bind to pyrimidine bases - blocks transcription
  and leads to cell death
• Abundant in Apiaceae
• Urushiol in poison ivy

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Urushiol
Poison ivy urushiol
Poison oak urushiol
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Coumarins

• Large group 1300 coumarins have been identified
• Basic coumarin is a 2 ring structure, phenol and
  pyrone
• Many anticoagulants including Warfarin

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Lignin a complex phenolic
Lignin monomers

• Polymer of three phenolic alochols
• Different species have different ratios of these
  monomers
• Lignin in beech has 100707 of coniferyl
  sinapyl para-coumaryl

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Flavinoids

• One of the largest classes of phenolics
• Carbon skeleton has 15 carbons with two benzene
  rings connected by a 3-C bridge

-C3-
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Flavinoids

• Flavinoids classified into different groups based
  on the degree of oxidation of the 3-C bridge
• Anthocyanins
• Flavones
• Flavonols
• Isoflavones
• Majority of flavinoids exist as glycosides

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Anthocyanins
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Tannins

• Tannin a general name for a large group of
  complex phenolic substances that are capable of
  tanning animal hides into leather by binding
  collagen

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Tetrahydrocannabinol