Gourt Home::Gourt :: Benzopyrene
| Benzopyrene | |
|---|---|
| Chemical name | Benzo*pyrene |
| Chemical formula | C20H12 |
| Molecular mass | 252.31 g/mol |
| CAS number | |
| Density | 1.24 g/cm3 |
| Melting point | 179 °C |
| Boiling point | 495 °C |
| SMILES | c1\cc2\cc/cc3ccc4cc5ccccc5c1c4c23 |
| Chemical infobox | |
BenzoC20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. It is a crystalline yellow solid. Benzo[apyrene is a product of incomplete combustion at temperatures between 300 and 600°C. Is found in coal tar, in automobile exhaust fumes (especially from diesel engines), tobacco smoke, and in charbroiled food. Recent studies have revealed that levels of benzopyrene in burnt toast are significantly higher than once thought, although it is unproven whether burnt toast is itself carcinogenic.
Consequences of Benzopyrene
A huge number of studies over the previous three decades have documented links between benzoand cancers. It has been more difficult to link cancers to specific benzoKansas State University recently discovered a link between vitamin A and emphysema in smokers. Benzo[a" target="_blank" >*pyrene was found to be the link to the deficiency, since it induces vitamin A deficiency in rats. On October 18, 1996, a study was published that provided the first true molecular evidence conclusively linking components in tobacco smoking to lung cancer. A chemical found in tobacco smoking, benzo*pyrene, was shown to cause genetic damage in lung cells that is identical to the damage observed in the DNA of most malignant lung tumours.
A 2001 National Cancer Institute study found levels of benzopyrene to be significantly higher in foods that were cooked well-done on the barbecue, particularly steaks, chicken with skin, and hamburgers. Japanese scientists showed that cooked beef contains mutagens, chemicals that are capable of altering the chemical structure of DNA.
Interaction with DNA
Benzodiol epoxide ((+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo*pyrene" target="_blank" >is first activated by cytochrome P4501A1 to form (+)-benzo*pyrene" target="_blank" >7,8-oxide is metabolized by epoxide hydrolase to yield (-)-benzo*pyrene-7,8,dihydrodiol" target="_blank" >forms the ultimate carcinogen after reacting with cytochrome P4501A1 to yield benzopyrene diol epoxide ((+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[apyrene). The two carbons of the epoxide are electrophilic, due to an unequal sharing of electrons with the oxygen. As a result, this molecule intercalates in DNA, covalently bonding to the nucleophilic guanine nucleobases at the N2 position. A recent X-ray crystallography study shows this distorts the DNA. This can disrupt the normal process of copying DNA, and may lead to cancer. This mechanism of action is similar to that of aflatoxin which binds to the N7 position of guanine.
Benzo*pyrene induces high concentrations of cytochrome P4501A1 (CYP1A1) by binding to the AhR (aromatic hydrocarbon receptor) in the cytosol. Upon binding the transformed receptor translocates to the nucleus where it dimerises with ARNT (aryl hydrocarbon nuclear traslocator) and then binds xenobiotic response elements (XREs) in DNA located upstream of certain genes. This process increases transcription of certain genes, notably CYP1A1, followed by increased CYP1A1 protein production. This process is similar to induction of CYP1A1 by certain polychlorinated biphenyls and dioxins.
Recently, Benzo*pyrene has been found to activate a transposon, LINE1, in humans (see reference).
References
Vilius Stribinskis and Kenneth S. Ramos (2006). Activation of Human Long Interspersed Nuclear Element 1 Retrotransposition by Benzo(a)pyrene, an Ubiquitous Environmental Carcinogen. Cancer Res 2006; 66: (5).
See also
External links
Carcinogens | Polycyclic aromatic hydrocarbons
Benzo(a)pyren | Benzopireno | Benzopyrène | Benzopirene | Benzpirēns | Benzopiren | Бензпирен
"Benzopyrene"