Secondary Metabolites and Building Blocks

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Primary and Secondary Metabolites
• Despite the extremely varied characteristics of living
organisms, the pathways for generally modifying and
synthesizing carbohydrates, proteins, fats, and nucleic
acids are essentially the same in all organisms, apart from
minor variations.
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Kingdom Plantae
Kingdom Animalia
Kingdom Fungi
Kingdom Bacteria
• These processes demonstrate the fundamental unity of all
living matter, and are collectively described as primary
metabolism, with the compounds involved in the pathways
being termed primary metabolites...i.e. CHM411 stuff 
Primary Metabolites
• Necessary for basic survival of an organism
• Used for energy and tissue construction
• Includes most carbohydrates, amino acids and
proteins, lipids, nucleic acids, and some
vitamins & cofactors
Secondary Metabolites
Resource: Dewick, Medicinal Natural Products, Ch. 2
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Are assembled from (pieces of) primary metabolites
Are plentiful and diverse in plant-based foods
May be more prevalent or unique to certain genus,
species, and similar compounds occur within genuses
and families
Often have vital functions in the source
• attractants for propagation of species
• defense against predators
• signaling
May have useful nutritional benefits to humans/other
organisms
The genes and enzymes guiding biosynthesis vary from
one organism to the next.
Origins of secondary
metabolites
Four major pathways to
assembly of C skeleton:
•acetate
•shikimate
•mevalonate (all organisms)
•DXP (plants, microbes)
Key precursors:
Phosphoenol pyruvate (PEP)
 shikimate pathway
Acetyl CoA  acetate or
mevalonate pathways
N from amino acids 
alkaloids
Building blocks (Fig. 2.2)
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C1 – methyl groups
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C2 – 2 carbon units from acetate pathway
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C5 – isoprene
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C6C3 - phenylpropanoid
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C6C2N – precursor to indole
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C4N & C5N – heterocyclic amines
C1: any molecule
C2: Fatty acids
Long chains on most
molecules
Polyketides
Some aromatic rings
C5: Isoprenoids
chains & nonarom.
rings
C6C3:
Phenylpropanoids
C1 comes from SAM (S-adenosylmethionine)
SAM can attach a methyl group to just about anything
Methyls may be attached to C atoms on chains, rings,
attached to oxygen (methoxy),
attached to nitrogen (N-methyl)
Building blocks (Fig. 2.2)
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C1 – methyl groups
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C2 – 2 carbon units from acetate pathway
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C5 – isoprene
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C6C3 - phenylpropanoid
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C6C2N – precursor to indole
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C4N & C5N – heterocyclic amines
Origins of alkaloids
(nitrogen-containing natural products)
pyrrolidine
piperidine
Identify the building blocks
• Most secondary metabolites are assembled
from pieces coming from more than one
biosynthetic pathway
• Can you figure out what the building blocks
are in each structure?
• Analysis of building blocks helps us
understand how the compound was made,
what were the precursors?
b-carotene
resveratrol
linolenic acid
a-bisabolene

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