Transcript Lecture 02 - Natural products & biosynthesis, web

Bratton, Heather
Bautista, Candie
Bui, Steven
Chen, John
Chem 444
Biol 444
Chan, Hiu Fai
Chida, Odette
Doan, Chad
Cueva, Carla
Ho, Joyce
Golanbar, Gelareh
Karimbabai Massihi, Anna
Kashiwabara, Claudine
Krasner, Danielle
Kopilec, Jaimisyn
Loi, William
Lau, Jensen
Malette, Jacqueline
Le, Giang-Tuong
Nguyen, Trang
Lee, Margaret
Robles, Marisa
Mata, Francisca
Tallorin, Lorillee
Nguyen, Thuy Nhi
Truong, Daniel C
Phillips, Irving
Udeh, Francis
Romero, Marcelo
Villalvazo, Adrianne
Wang, Tony
Yeh, Enrenn
Wittig, Michelle
Primary (1°) Metabolism
- Construct common biological macromolecules from simple
building blocks found within every cell
- Typically a process of polymerization, stringing monomers
together into a macromolecule that performs a cellular function
sugars
polysaccharides
amino acids
proteins
fats
phospholipid bilayers
- Block production: cell dies (primary metabolites are essential)
Secondary (2°) Metabolism
- Synthesize compounds that are unique to a particular species
or genus (unlike common proteins, lipids, etc.)
- Molecules may have extremely complex structures
- These molecules typically have no effect on the producing
organism, but are often highly biologically active against
other organisms (competitors, pathogens, predators)
- Often present at extraordinary concentrations, >10%
of the dry weight of the organism
inference is, they must do something
Natural Products: Folk to Modern Medicines
- Humans have long used chemicals in plant and animal extracts
for many purposes: medicines, poisons, recreational stimulants
- Since the 1800’s, chemists have characterized and synthesized
such natural products, uncovering the basis for folk remedies
- Identifying the mechanism of action of natural products was
the genesis of modern drug discovery
- The active ingredients in many ancient curatives are still used
medicinally today
Natural Products 1: Toxins
Rotenone
- Natural fish + insect poison
Curare (Tubocurarine chloride)
- Derived from 2 South American plant genera
- Used as arrow-tip poison by native peoples
- Blocks transmission of acetylcholine signal to muscles, causing
instant paralysis
- 1st drug used as muscle relaxant in surgery
Natural Products 1: Toxins
Hyoscine (= scopolamine)
- Derived from plants: deadly nightshade (belladonna), mandrake
- In ancient Greece, mandrake was used as an anaesthetic
(or poison, in higher doses)
- “Witches” smeared extracts on their armpits: avoided toxic oral route,
got maximum hallucinogenic effect = felt like they were flying
- Blocks certain acetylcholine receptors
- Modern use: prevention of motion sickness (patches behind the ear)
Natural Products 2: Medicines
COCH3
Salicin
Acetyl-salicilic acid: aspirin
- From Willow tree bark, which was used in folk remedies
for treating fevers
- Led to synthetic analogue, modern aspirin
Natural Products 2: Medicines
Ventolin
Ephedrine
- From Ephedra plants, basis of ancient Chinese herbal remedy
“Ma Huang” (100 AD) for treating respiratory illness
- Used clinically since 1926 as bronchodilator to treat asthma
- Similar to adrenaline, but also stimulates heart (not good in a drug)
- Stimulated research resulting in the non-stimulant drug Ventolin
Natural Products 2: Medicines
Quinine
- Found exclusively in the bark of the Chinona tree
- Used as a malaria treatment since 1600’s
- Now synthetic derivatives used, due to widespread resistance
Natural Products 3: Stimulants
Caffeine
Nicotine
- Caffeine-containing plant leaves + seeds have long been brewed to
produce stimulant drinks
- Such stimulants naturally act as feeding deterrents to repel insect
herbivores that consume plants leaves
- Tobacco plant can up its production of nicotine 4-fold when under
attack by insects; nicotine by-products are used as insecticides
Natural Products 3: Stimulants
Cocaine
- Coca leaves have been used as a source of cocaine for > 2,000 yrs
- Used by Incas in religious ceremonies
- Introduced to Europe by conquistadores
- Leaves chewed daily by >8 million native peoples in the Andes,
to alleviate feelings of hunger and fatigue
- Inhibits re-uptake of excitatory neurotransmitter dopamine
Natural Products 4: Halucinogens
Morphine (= opium)
Heroin (synthetic derivative)
- Found in only 2 species of poppy flower (Papaver)
- Milky exudate of seed capsules is 25% opiate
- Used as a baby calming treatment in ancient Egypt
- Binds to brain receptors for short peptides called enkephalins,
derived from endorphins
Natural Products 4: Halucinogens
Similar spatial relationships of
(*)-marked atoms responsible for
similar pharmacological effects
Enkephalin
Morphine
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Natural Products 4: Halucinogens
Tetrahydrocannabinol
Lysergic acid
- Lysergic acid is the parent compound from
which ergot alkaloids are derived, such as LSD
Lysergic acid
Diethylamine
(LSD, synthetic)
- Produced by fungus; often affected stored grain in Middle Ages
- Such compounds found in Aztec “magical” preparation ololuiqui
- Structural mimics of human neurotransmitter 5-hydroxytryptamine
Secondary Metabolites
- Produced from a small number of key intermediates, often
generated as by-products of primary metabolism
acetate (in the form of acetyl coA)
mevalonate
4-carbon sugars
- Perhaps arose as a means of dealing with excess metabolic
intermediary compounds
-2o metabolites then took on ecological roles as toxins, etc.
Secondary Metabolites
- Typically play ecological roles in nature, deterring would-be
pests, predators or pathogens
- Affect humans due to structural resemblance to innate
neurotransmitters, or by binding to proteins in a way that
disrupts normal cellular function
- Natural products are the basis for a big % of pharmaceutical
drugs currently on the market
-
Simple building blocks serve as the basis for each major
pathway of secondary metabolism:
(1)
Shikimate
Aromatics (ring - C3 chain)
(2)
Amino acids
Alkaloids, Penicillins
(N-containing)
(3)
Mevalonate
Terpenes, Steroids
(4)
Acetate
Polyketides
(aromatics, macrocycles)
(photosynthesis)
Polysaccharides
Glycosides
Nucleic Acids
phosphoenol
pyruvate
Shikimate pathway
Aromatic Compounds
Lignans
Shikimate
pyruvate
acetyl
CoA CH3COSCoA
aromatic amino acids
aliphatic amino acids
CITRIC
ACID
CYCLE
(1)
Alkaloids (2)
Peptides
Penicillins
Cyclic Peptides
CH3COSCoA
-O
2CCH2COSCoA
CH3COCH2COSCoA
CH3COSCoA
CH3COSCoA
mevalonate
Polyketides, Fatty Acids
Isoprenoids (terpenes, steroids,
(3)
carotenoids)
(4)
Prostaglandins, Macrocyclic Antibiotics
(1) Shikimate pathway
from the Japanese flower shikimi (シキミ, Illicium anisatum)
(A) Biosynthesis of aromatic amino acids (tyrosine,
phenylalanine, and tryptophan)
lead to alkaloids
(B) Build aromatic secondary metabolites
Shikimate
Podophyllotoxin
Shikimate biosynthesis
Shikimate + PEP
Chorismate
Prephenate
Other
shikimate
metabolites:
ring-C3
...ring-C2
...ring-C1
+ NH3
Cinnamic
acid
- NH3
Tyrosine,
Phenylalanine
Biosynthesis of phenyl compounds
ring-C1 type
vanillin
vanillic acid
salicin
salicylic acid
- In plants, many shikimate metabolites are allelopathic:
they inhibit growth of competitors
- Insoluble forms often linked to sugars in plant tissue
- Soluble acidic forms leach out into surrounding soil in rain
phenylalanine
Lignans & Lignins
Cinnamic
acid
Polymerization:
complex lignins
Enzymatic coupling:
dimeric lignans
Cinnamyl
alcohol
Podophyllotoxin
Large % of
woody plant
biomass
Podophyllotoxin
- An important shikimate compound
- Used by native Americans to cure warts
- Powerful inhibitor of mitosis; found to
block enzyme tubulin polymerase
-
-
Flavanoid Biosynthesis
Shikimate + 3 acetates = flavanones
Cause bitter tastes in plants,
especially polymerized tannins;
deter feeding by herbivores
Derived compounds are
responsible for much of plant
color
(2) Alkaloids
(2)
Amino acids
Alkaloids, Peptides, Penicillins
Penicillin
Strychnine
(alkaloid)
Cyclosporin A
(cyclic peptide)
Alkaloid characteristics
- Non-(normal)-peptide, non-nucleic acid compounds that
contain nitrogen
- Common in fungi, plants, insects + amphibians
- Derived from amino acid precursors
Tyramine
Tyrosine
Dopamine
Mescaline
- potent hallucinogen from the peyote cactus
- competitively binds to dopamine receptors
Penicillin Biosynthesis
a-adipate
+
cysteine
+
valine
- start with peptide made of 3 amino acids
(including a non-standard a.a., a-adipate)
a-adipate
+
cysteine
+
valine
isopenicillin synthase
penicillin N
epimerase
isopenicillin N
cephalosporins
penicillins
Penicillins: Mechanism of Action
This class of antibiotics interferes with synthesis of the cell wall
of Gram-positive bacteria (Staphylococci, Streptococci)
Cell wall is a repeating polymer of disaccharide, tetrapeptide
repeats cross-linked into a 3D matrix
(1) cleave here
(transpeptidase)
sugar - sugar - phospholipid
L-ala
— D-glu — L-lys — D-ala — D-ala
(glycine)5
(2) cross-link here
Penicillins: Mechanism of Action
Penicillins inhibit the bacterial transpeptidase enzyme by
mimicking its natural substrate, the terminal D-ala—D-ala
Transpeptidase attacks the b-lactam ring of penicillin, forms a
covalent bond; enzyme is now out of business
(1) NO CLASS next Monday
(2) For NEXT WEDNESDAY –
- bring to class a small amount of some spice, seeds, leaves,
fruit, or medicinal herb
- pick something with a strong taste/smell, or that you
know is used in a folk remedy
- at Wednesday’s lecture, you will put your material in a tube
and label it; I will then add solvent and extract the natural
products from it over the weekend
- in the next lab, you will bioassay the extracts of your material
for antibiotic activity and cytotoxicity