Bratton, Heather

Bui, Steven Chan, Hiu Fai Doan, Chad Ho, Joyce Karimbabai Massihi, Anna Krasner, Danielle Loi, William Malette, Jacqueline Nguyen, Trang Robles, Marisa Tallorin, Lorillee Truong, Daniel C Udeh, Francis Villalvazo, Adrianne Yeh, Enrenn

Bautista, Candie

Chen, John Chida, Odette Cueva, Carla Golanbar, Gelareh

Kashiwabara, Claudine Kopilec, Jaimisyn Lau, Jensen

Le, Giang-Tuong Lee, Margaret

Mata, Francisca Nguyen, Thuy Nhi

Phillips, Irving Romero, Marcelo Wang, Tony Wittig, Michelle

Biol 444Chem 444

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

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

Rotenone

- Natural fish + insect poison

Natural Products 1: Toxins

- 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)

Hyoscine (= scopolamine)

Natural Products 2: Medicines

Salicin

COCH3

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

- 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

Ephedrine

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-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

Caffeine Nicotine

Natural Products 3: Stimulants

- 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

Cocaine

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

MorphineEnkephalin

*

**

*

Similar spatial relationships of

(*)-marked atoms responsible for

similar pharmacological effects

Natural Products 4: Halucinogens

- Lysergic acid is the parent compound from which ergot alkaloids are derived, such as LSD

- 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

Lysergic acidTetrahydrocannabinol

Lysergic acid Diethylamine(LSD, synthetic)

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)mevalonate4-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)

PolysaccharidesGlycosidesNucleic Acids

Shikimate pathwayAromatic CompoundsLignans

aromatic amino acidsaliphatic amino acids

CH3COSCoA

CH3COSCoA

(photosynthesis)

phosphoenol pyruvate

pyruvate

acetylCoA CH3COSCoA

-O2CCH2COSCoA

CH3COSCoA

Polyketides, Fatty Acids Prostaglandins, Macrocyclic Antibiotics

Shikimate

CH3COCH2COSCoA

mevalonate

Isoprenoids (terpenes, steroids, carotenoids)

AlkaloidsPeptidesPenicillinsCyclic Peptides

CITRICACIDCYCLE

(1)

(2)

(3) (4)

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

Podophyllotoxin

(1) Shikimate pathway

Shikimate

Shikimate biosynthesisChorismateShikimate + PEP

Prephenate

+ NH3

Tyrosine,Phenylalanine

- NH3Cinnamic

acid

Other shikimatemetabolites:

ring-C3

...ring-C2

...ring-C1

Biosynthesis of phenyl compounds

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

ring-C1 type

Lignans & Lignins

Podophyllotoxin

Polymerization:complex lignins

Cinnamyl alcohol

Large % ofwoody plant biomass

Enzymatic coupling:dimeric lignans

phenylalanine

Cinnamic acid

Podophyllotoxin

- An important shikimate compound

- Used by native Americans to cure warts

- Powerful inhibitor of mitosis; found to block enzyme tubulin polymerase

-

-

-

Flavanoid BiosynthesisShikimate + 3 acetates = flavanones

Cause bitter tastes in plants,especially polymerized tannins; deter feeding by herbivores

Derived compounds are responsible for much of plantcolor

(2) Amino acids Alkaloids, Peptides, Penicillins

Penicillin

Cyclosporin A(cyclic peptide)

Strychnine(alkaloid)

(2) Alkaloids

Alkaloid characteristics

- Non-(normal)-peptide, non-nucleic acid compounds that contain nitrogen - Common in fungi, plants, insects + amphibians

- Derived from amino acid precursors

Tyrosine

Tyramine

Dopamine

Mescaline

- potent hallucinogen from the peyote cactus

- competitively binds to dopamine receptors

-adipate

+

cysteine

+

valine

Penicillin Biosynthesis

- start with peptide made of 3 amino acids (including a non-standard a.a., -adipate)

-adipate +cysteine +valine

isopenicillin synthase

epimerasepenicillin Nisopenicillin N

penicillinscephalosporins

Penicillins: Mechanism of ActionThis 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

sugar - sugar - phospholipid

L-ala — D-glu — L-lys — D-ala — D-ala

(glycine)5

(1) cleave here (transpeptidase)

(2) cross-link here

Penicillins: Mechanism of ActionPenicillins inhibit the bacterial transpeptidase enzyme by mimicking its natural substrate, the terminal D-ala—D-ala

Transpeptidase attacks the -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