Transcript diol epoxide - MyLinh`s Organic Chemistry Website

The CANCER RISK of
BENZO[α] PYRENE
Abstract # 30
Presented by My Linh Tran
Math and Science Division
San Jose City College
Spring 2006
Instructor Dr. Adamczeski,Madeline
ABSTRACT
When people eat burnt barbequed food, they may carelessly
consume significant amounts of carcinogens, some of which called
aromatic hydrocarbons. The definition of aromatic hydrocarbon can
be extended from simple one ring to substances that have two or
more benzene-like rings joined together by common bonds (e.g.
polycyclic aromatic hydrocarbons). Benzopyrene (BaP) is
categorized as a polycyclic aromatic hydrocarbon and is recognized
as one of the most carcinogenic of the group. BaP is formed from a
reaction between one of the twenty essential amino acids and
creatine in the process of cooking meats at high temperature.
Creatine is an amino acid that does not occur in protein but is found
in the muscle tissues of vertebrates both in the free form and as
phosphocreatine (e.g. it supplies energy for muscle contraction).
After eating BaP, our body attempts to rid of the foreign substance
by converting it into a water-soluble compound for metabolism, a
diol expoxide. This compound, in turn, reacts with and binds to
cellular DNA. Consequently, diol expoxide alters DNA and mutates
genes. This presentation introduces BaP, shows reaction
mechanism involving BaP, and explains how BaP can cause cancer.
Benzopyrene- Polycyclic Aromatic
Hydrocarbons and Mutations
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Seminar Outline
Introduction:
What is Benzopyrene?
Burnt barbeque, meat, fish,
How is it made?
Where can we find it
Structure
C20H12
Toxicity data research
Epoxidation
Chemical evaluation
Properties:
Benzene
Flat, sp2, conjugated pi electrons
Stable
Reacts with oxygen and other electrophiles
Biological evaluation
Metabolism:
Liver MFO enzyme
Water-soluble epoxy groups
Reactions with epoxy groups
Epoxides of benzopyrene
DNA mutation
It becomes similar to dA and dG
General information
Dose
Duration
Pathway
Individual
VI.
Conclusion
The dose makes the poison
BBQ at low temperature
Use thinner slice of meat
Teriyaki sauce or turmeric-garlic sauce before barbeque
SUMMER BARBEQUE
WOULD YOU EAT THIS?
The well known Polycyclic Aromatic Hydrocarbon
OVERVIEW
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Introduction
What is Benzo[α]pyrene?
Chemical properties
What is its effect on
humans?
• How is it made?
• Where can we find it?
• Prevention
BENZO[α]PERENE (BaP)
•Yellow crystals or Powder
•Molecular formula: C20H12
•Formula weight: 252.31 amu
•CAS No: 50-32-8
•Boiling point: 495 oC
•Melting point: 176 oC
•RAT LD50 50mg / kg
•MOUSE LDLO 500mg / kg
•FROG LDLO 11 mg/kg
BARBEQUE and POLYCYCLIC and
CANCER
• SOURCE: BURNT Barbeque
• EFFECT: Formed from a reaction between amino
acids and creatine when meats are cooked at high
temperature
• Creatine: an amino acid that does not occur in
proteins but is found in the muscle tissue of
vertebrates both in the free form and as
phosphocreatine; supplies energy for muscle
contraction
• CONSEQUENCE: MUTATION
HOW BaP CAUSE
MUTATIONS?
• After eating or inhaling, body attempts to rid itself of the
foreign substance by converting it into a water-soluble
metabolism: DIOL EXPOXIDE
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DIOL EXPOXIDE Metabolite reacts with & binds to
cellular DNA
• DIOL EXPOXIDE altering the DNA & leading to mutations
or cancers
STABILITY OF BaP
• Stable, incompatible with strong oxidizing
agents
• Causes oxidation, gain one or more
electrons, undergoes reduction, oxidation
number of atom decrease
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PERCHLORATES
PEROXIDES
PERMANGANATES
CHLORATES
NITRATES
CHLORINE
BROMINE
FLOURINE
BaP- SITE of EPOXIDATION
http://www.nyu.edu/projects/geacintov/images/WEB
_Figures/WEB_PAH2.jpg
SIMILAR to the BASES THEY REPLACE
HYDROLYSIS of EPOXIDE
DIOL EPOXIDE HYDROLASE
(R,S,S,R) enantiomer:
On reaction with DNA, DE derived (BaP) are largely
selective for G adduct formation
DIOL EPOXIDE
DNA- DIOL EPOXIDE
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Altered DNA by replication
Altered RNA by transcription
Incorrect protein synthesis
Shortened DNA by replication through blockage
Shortened RNA by transcription blockage
HOW ARE WE EXPOSED TO BaP?
• Breathing air contaminated by smoke from incomplete
combustion & vehicle exhaust
• Eating meats and fish that have been smokes or
charbroiled
• Smoking tobacco products
WHERE BaP CAN BE FOUND?
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Wildfires and Control burning
Combustion engine vehicles
Charbroiled meat
Burning or scrap tires
BaP ENVIRONMENTAL INFORMATION
Very toxic in the environmentmay cause long-term damage
BaP is not produced
commercially in the United
States except as research
chemical
BaP has decreased it
emission over last 13 years
Emissions from Prodtion
Processes have reduced
greatest
PREVENTIONS
• Barbecue meat at low temperatures, do not
overcook
• Use thinner slices of meat (they cook faster and
with less heat)
• Turn the meat more frequently
• Teriyaki sauce or turmeric-garlic sauce before
barbeque
• Marinade before grilling
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