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9.3: Functions and Applications of Amines

Difficulty Level: At Grade Created by: CK-12
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Heterocyclic Amines and Cancer

Heterocyclic amines (HCAs) are commonly found in cooked meat, especially if the meat has been cooked at extremely high temperatures. They are the product of a reaction between amino acids and creatine, a chemical found in muscles. Cooking meats such as beef, pork, fowl, and fish creates heterocyclic amines that are not present in the uncooked form of these meats.

Heterocyclic amines are common in cooked meat.

Scientists have found a strong link between heterocyclic amines and cancer. Seventeen different heterocyclic amines present in cooked meats have been found to cause cancer in humans. In one study, scientists surveyed the diets and cooking habits of 176 people diagnosed with stomach cancer and 503 people without cancer. They discovered that people who ate their beef “well done” or “medium well” were three times more likely to develop stomach cancer than those who ate their beef “rare” or “medium rare.” They also found that people who ate beef frequently – four or more times a week – were twice more likely to develop stomach cancer than those who ate beef less frequently. Other studies have found links between eating barbecued, fried, and well-done meats with colorectal, pancreatic, and breast cancer.

High temperatures are essential for the production of heterocyclic amines. This is because every reaction requires a minimum amount of energy, known as activation energy, for the reaction to proceed. For amino acids and creatine to react to form HCAs, large amounts of energy in the form of heat are required. That is why scientists found that frying, broiling, and barbecuing meats produce the largest amount of HCAs. All three of these methods require extremely high temperatures. One study showed the importance of temperature on the production of heterocyclic amines. Researchers found that when the temperature was increased from 200oC to 250oC (392oF to 482oF) the amount of HCAs produced was increased threefold.

There are many ways to decrease HCA intake in your life, and, by doing so, your cancer risk. Eating less meat or “rarer” meat will decrease the amount of HCA that is consumed. Another way would be to partially cook the meat in a microwave oven before it is cooked. Two minutes of microwaving before cooking decreases the HCA amount by 90%. Pouring out the liquid that forms when the meat is heated in the microwave also decreases the heterocyclic amine count. Marinating the meat before it is cooked also destroys HCA production. Marinating meat in olive oil, lemon juice, and garlic, besides enhancing the taste, cuts the HCA levels in chicken by as much as 90%. A beer or red-wine marinade also achieves this effect. This could be because beer and red wine contain water-retaining sugars. These sugars, once in the meat, attach onto the water. This hinders the movement of water-soluble molecules that depend on water for movement. If these molecules do not get to the surface of the meat, the heat is not great enough to turn them into HCAs.

Histamine and Allergies

Many amines are present in the body as neurotransmitters. One important example is histamine. This is an amine that helps the brain cells communicate properly and modulates sleep. However, histamine is most known for its connection with allergies. Allergies happen when a normally harmless substance like pollen or dust, known as an allergen, enters the body. When it comes in contact with the antibody IgE, it triggers a reaction that signals for the release of histamine. Histamine binds onto nearby cell receptors, causing many of the symptoms that are associated with allergies: swelling of the infected area, shortness of breath caused by swelling of the mucous membranes, and muscle cramps. These allergic reactions can be mildly annoying or life-threatening, depending on the severity.

Many people are allergic to the histamines and other amines that are present in foods. Food-related histamine reactions have the following symptoms: flushing of the face, sudden sweating, fainting, asthma attack, rash, hives, urticaria, nausea, vomiting, abdominal cramps, headaches, and migraine attacks. These reactions to histamines in foods are generally more severe than the respiratory reactions to allergens.

To see a video about the connection between histamines and allergies, watch this video:


Fortunately, there are different medicines that work to counteract the body’s unnecessary production of histamines. Many of these medicines are antihistamines. They work by binding onto cell receptors, preventing histamines from binding there. If histamine does not reach the cell receptors, it cannot cause the many symptoms of allergies.

Trimethylamine and Trimethylaminuria

Like many classic amines, trimethylamine has a strong, rancid odor that is responsible for the “fishy” smell of fish. Although smelly, this molecule is completely harmless.

Trimethylaminuria is the disease associated with the body’s inability to break down trimethylamine. Normally, the body is able to convert trimethylamine into a compound called trimethylamine N-oxide that is considerably less smelly. However, if the enzyme FMO3 is impaired or malfunctioning, this conversion will not happen and the body will be left with excess amounts of trimethylamine. This excess is released into the person’s sweat, urine, reproductive fluids, and breath.

This disease is inherited in an autosomal recessive function, which means that the gene responsible for this disease is recessive. It would take two trimethylaminuria genes for a person to show symptoms for the disease. Having just one of the genes would make a person a carrier for trimethylminuria; they would show no symptoms.

Only people with two recessive trimethylaminuria genes will exhibit the symptoms.

Besides its smelly side effects, trimethylaminuria is not a particularly life-threatening disease. This is fortunate because currently there is no known cure for this disease. Someone diagnosed with trimethylaminuria can decrease the effects of the disease by avoiding foods that contain trimethylamine. These foods include eggs, liver, kidney, peas, beans, peanuts, soy products, brassicas (brussel sprouts, broccoli, cabbage, etc), and lecithin and lecithin-containing fish oil supplements.

Another way to decrease the effects of trimethylaminuria would be to use soaps with a moderate pH between 5.5 to 6.5. This is because trimethylamine, due to the lone electron pair on its nitrogen, is a base with a 9.8 pH. Therefore, a more moderate soap would neutralize the trimethylamine better than a basic soap. Washing with a slightly acidic soap makes it easier to remove any trimethylamine lingering on the skin.

Aniline’s Toxicity

Aniline, also known as aminobenzene, is an amine that is essential for creating many industrial chemicals. It is produced in huge amounts in the United States; in 1992 alone, one billion pounds of aniline were produced. Since then, demand for aniline-containing chemicals has increased, causing the production of aniline to skyrocket. Aniline is used to create isocyanates, dyes, drugs, rubbers, pesticides, photographic chemicals, varnishes, and explosives. Aniline is a somewhat toxic chemical that has harmful effects on the environment and human health.

There are many ways that aniline can be released into the environment, but once there, it is quickly broken down into less harmful molecules. When exposed to the air, aniline will evaporate. Once it gets into the environment, sunshine and microorganisms break it down. However, aniline is soluble in water and is toxic to aquatic life. If raw aniline were to reach a water source, it would be detrimental to the aquatic life there.

In small amounts, aniline is harmless to humans because it is does not remain in the body. However, humans consistently exposed for several years to small amounts of aniline in the air have experienced adverse blood effects. A short exposure to large amounts of aniline affects the hemoglobin and makes it difficult for hemoglobin to carry oxygen throughout the body. Side effects from this can range from headaches to comas and death. Single exposures can also affect the spleen, but these effects can usually be reversed by proper treatment. In the United States, people are not usually exposed to the levels of aniline needed to have adverse side effects on the body.

Gefitinib and Medicine

Gefitinib is an amine-containing drug that is marketed to help patients suffering from non-small cell lung cancer. It is part of a group of drugs called epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. This class of anti-cancer medication works by blocking the production of certain chemicals that help cancerous tumors grow.

Gefitinib works by preventing the phosphorylation of a receptor found on normal and cancer cells. Phosphorylation is the addition of a phosphate group. It is responsible for the activation and deactivation of many proteins enzymes. By preventing phosphorylation, gefitinib can stop the growth cancer cells.

However, it is neither a miracle pill nor a guaranteed cure. The effects of Gefitinib vary from person to person. It could work for someone, but be completely useless to another. Gefitinib should only be taken after all other treatments have been ineffective. link title

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