What Are Heterocyclic Amines?

Heterocyclic amines: At the end of the 1970s, it was found that compounds extracted from the charring surface of grilled fish or roast beef were mutagenic. Studies on the main mutagens in grilled fish showed that these materials are mainly complex heterocyclic amines. Heterocyclic amines, for example, Imidazoquinoline (IQ) and Methylimida-zoquinoline (MelQx). These substances are also the main components of mutagenic substances in fried beef extract

Heterocyclic amines: At the end of the 1970s, it was found that compounds extracted from the charring surface of grilled fish or roast beef were mutagenic. Studies on the main mutagens in grilled fish showed that these materials are mainly complex heterocyclic amines. Heterocyclic amines, for example, Imidazoquinoline (IQ) and Methylimida-zoquinoline (MelQx). These substances are also the main components of mutagenic substances in fried beef extract

Figure 4-26 Structure of heterocyclic amine

Beef extract is metabolized into active mutagens in several experimental animals and human liver tissues. Although such substances were found to be highly potential mutagens in the Ames test, they appeared to be weak in rats Carcinogenicity.

When cooking protein-rich foods, the degradation products of proteins, tryptophan and glutamic acid, first form a group of polycyclic aromatic amine compounds, such as tryptophan pyrolysis products (Trp-p-1 and Trp-p-2 ) And glutamine pyrolysis products (Glu-pl). Teratogenic studies have found that pyrolysis products of tryptamine and glutamine are mutagenic to rats, hamsters and mouse animals. For example, mice fed Trp- Increased tumor incidence was observed after pl or Trp-p-2 drinks. Some other reports indicate that the pyrolysis of amino acids and proteins appears to be carcinogenic to the digestive tract of experimental animals. However, other protein-rich foods such as milk, Cheese, tofu and various legumes are only slightly mutagenic, although severely carbonized when treated at high temperature. In addition, the degree of heating also affects the level of mutagenic activity. Further research is ongoing to confirm whether heterocyclic amines are cooking The process produces substances that are harmful to humans.

Heterocyclic Amine Toxicology

Heterocyclic amine mutagenesis

One of the major hazards of heterocyclic amines is their mutagenicity. However, heterocyclic amines are indirect mutagens, and they are mutagenic only by metabolic activation under the action of cytochrome P450. The active metabolites of heterocyclic amines are N-hydroxy compounds. Monohydroxy metabolites are converted into terminal mutants. Ames test shows that heterocyclic amines have strong mutagenicity in the S9 metabolic activation system, of which TA98 is more sensitive than TAl00. It is suggested that heterocyclic amines are frame-shifting mutants. In addition to inducing bacterial gene mutations, heterocyclic amines can also induce DNA damage in mammalian cells through the S9 activation system, including gene mutations, chromosomal aberrations, sister chromosomal exchange, DNA breaks, DNA repair synthesis, and oncogene activation. However, heterocyclic amines are less mutagenic in mammalian cell systems than bacterial systems ^[1] .

Carcinogenicity of heterocyclic amines

Another important hazard of heterocyclic amines is carcinogenesis. Heterocyclic amine compounds are carcinogenic to rodents to varying degrees. The main target organs for carcinogenesis are the liver, followed by blood vessels, intestines, foreguts, breasts, clitoral glands, lymphoid tissues, skin, and oral cavity. IQ has recently been found to be carcinogenic to primates ^[1] .

Heterocyclic amine myotoxicity

In addition to heterocyclic amine compounds that are mutagenic and carcinogenic, some heterocyclic amines such as IQ and PhIP form high levels of adducts in the heart of non-carcinogenic target organs. Studies have found that 8 rats were orally ingested IQ and PhIP for 2 weeks. Seven of them showed myocardial tissue microscopic changes, including focal myocardial cell necrosis with chronic inflammation, myofibrillarization and misalignment, and T-tubule dilatation. Another study reported the results of cardiac histopathological examination of monkeys who were only treated with IQ chronic carcinogenesis. These monkeys had liver tumors after ingesting IQ10 or 20 mg / kg for 40 to 80 months. The hearts of all animals were unchanged in appearance, but the hearts of eight monkeys were focally damaged under the microscope. Light microscopy showed muscle cell necrosis with or without inflammatory myofibrils disappearing and sarcomere arrangement disorder. The severity of myocardial injury is related to the cumulative dose of IQ ^[1] .

Heterocyclic amines prevent food contamination by heterocyclic amines

(1) Changing bad cooking methods and eating habits The generation of heterocyclic amine compounds is related to poor cooking and processing methods, especially when cooking foods at too high temperatures can produce more heterocyclic amine compounds. Therefore, care should be taken not to make the cooking temperature too high, not to burn the food, and to avoid eating too much grilled and fried food. Use cooking methods that reduce the production of heterocyclic amines, such as boiling, steam, and microwave cooking. Microwave treatment of meat before cooking can significantly reduce the production of heterocyclic amine precursor creatine, thereby reducing the production of heterocyclic amines; frying fish with a layer of starch and frying can also prevent heterocyclics Formation of amines.

(2) Increasing the intake of vegetables and fruits Dietary fiber has the effect of adsorbing heterocyclic amines and reducing their activity. Certain substances in vegetables and fruits, such as phenols, flavones, and other active ingredients can inhibit the mutagenicity and carcinogenicity of heterocyclic amines. Therefore, increasing the intake of vegetables and fruits has a positive effect on preventing the harm of heterocyclic amines.

(3) Inactivation treatment Hypochlorous acid, peroxidase and other treatments can oxidize and inactivate heterocyclic amines, and linoleic acid can reduce the mutagenicity of heterocyclic amines.

(4) Strengthening monitoring On the one hand, it is necessary to establish and improve the detection method of heterocyclic amines and strengthen the monitoring of heterocyclic amine content in foods; at the same time, further studies on the generation of heterocyclic amines and their influencing factors, metabolism in vivo, toxicity and The threshold dose, etc., establish the allowable limit standard for heterocyclic amines in food as soon as possible. ^[1]