Why are certain epoxides dangerous?

1 Answer
May 6, 2017

Epoxides are carcinogenic because they disrupt our DNA.

Explanation:

Epoxides are three-membered cyclic ethers.

Epoxide

They are highly strained because the nominal bond angles are 60° instead of 109.5°.

They tend to react with other molecules to open the ring and reduce the strain.

A common pro-carcinogen is benzo[a]pyrene.

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It is a constituent of automobile exhaust, smog, cigarette smoke and charcoal-cooked foods.

When the body absorbs benzo[a]pyrene, it tries to make it water-soluble so it can be excreted in the urine or feces.

Benzopyrene metabolism
(From researcgate.net)

It converts the benzo[a]pyrene into benzo[a]pyrene-7,8-epoxide.

This is hydrolyzed to the 7,8-dihydrodiol, which is further converted into benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide.

Once formed, the epoxide can π stack with the bases in DNA where the epoxide group reacts with guanine residues.

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This distorts the structure of DNA and causes errors in DNA replication.

If these mutations occur in a gene that encodes a molecule that regulates the production of cells, the result may be cancer.