Mutagens pyrolysis

The involvement of tobacco smoke carcinogens in the aetiology of lung cancer is conclusively established, but the role of specific chemical carcinogens as inducers of colorectal cancer is much less clear. Mutagenic pyrolysis products derived from cooked food have come under suspicion as possible... 

Dean, M. A., A. S. Dhaliwal, and W. R. Jones. Effects of Zingiberaceae rhizome extract of the infectivity of cyanophage LPP-1. Trans 111 State Acad Sci Suppl 1987 80 Abstr 83. Morita, K., M. Hara, and T. Kada. Studies on natural desmutagens screening for vegetable and fruits factors active in inactivation of mutagenic pyrolysis products from amino acids. Agr Biol Chem 1978 42(6) 1235-1238. 

Methods were described for HPLC determination of the mutagenic and carcinogenic a-carbolines (56,57), y-carbolines (58,59)155 160, and other products of amino acid pyrolysis found in cigarette smoke, diesel exhaust and cooked foods and phenazines (60, 61) present as impurities of certain pesticides161. These compounds were also determined in human plasma, urine and bile161,162. 

Presently about 20 different mutagenic and/or carcinogenic heterocyclic amines (HAs) have been isolated from various heat-processed foods. One class of these HAs is formed by pyrolysis of proteins or some amino acids. These HAs are amino-carbolines (Figure 13.7), and have been identified in grilled, broiled, baked, and fried meat and fish products, in meat sauces and bouillons, as well as in pyrolyzed proteins, glutamate, lysine, phenylalanine, tryptophan, ornithine, and creatine. 

Polycyclic aromatic hydrocarbons (PAHs) represent a heterogeneous class of environmental contaminants formed by incomplete combustion or pyrolysis of organic matter. They comprise compounds with 2-6 fused benzene rings, most of which (4-6 ring compounds) are known human mutagens and carcinogens. 

Subsequent epidemiological studies have supported the association between better health and long-term consumption of diets rich in foods of plant origin. " However, whether this is because such diets minimize exposure to deleterious substances (e.g., oxidized cholesterol, pyrolysis mutagens, salt, saturated fat, etc.), or maximize intake of certain beneficial nutrients (e.g., isothiocyanates and other sulfur-containing plant constituents, mono-unsaturated fatty acids, and poly-unsaturated fatty acids, PPT, poly acetylenes, selenium, terpenes, etc.) or some combination as advocated in the Polymeal concept, remains unknown. " An in vitro study indicates that there may be mechanistic basis for true synergy between PPT and isothiocyanates. ... 

Table I. Mutagenic activity of condensate of smoke formed by pyrolysis of biomacromolecules and of amino acids...

Table IV. Mutagenic activities of mutagens isolated from pyrolysis products and typical carcinogens...

Thus, by the Maillard reaction in different browning systems of sugars and amino compounds, some mutagenic substances were formed, although their activities are quite weak compared with those formed by pyrolysis of amino acids. They were confirmed as intermediates and some of them were identified as furan, pyrrole, or thiazolidine derivatives formed from glucose and amino acids... 

T. Sugimura, T. Kawachi, M. Nagao, T. Yahagi, Y. Seino, T. Okamoto, K. Shudo, T. Kosuge, K. Tsuji, K. Wakabayashi, Y. Iitaka, and A. Itai, Mutagenic principle(s) in tryptophan and phenylalanine pyrolysis products, Proc. Japan Acad., 1977, 53, 58-61. 

A special concern regarding the pyrolysis of Maillard polymers is the formation in this process of mutagenic compounds. Some of these compounds were isolated from pyrolysed food [5,6]. The formulas of several such compounds are shown below ... 

The association of Maillard polymer pyrolysis with the formation of these compounds is based on the correlation of the level of sugars and amino acids with the level of mutagen formation. Also, it was shown that the presence of creatinine (common in animals) may play an important role in the formation of these compounds, and a reaction path as shown below was proposed [19] ... 

Also pyrolysis has been used for differentiating different proteinaceous materials such as enzymes or microorganisms. Also, the generation of mutagenic compounds by pyrolysis of proteins has been of significant interest related to food and consumer products [2]. 

Besides the determination of major pyrolysis products for amino acids, a special issue is the formation of several mutagenic compounds (heterocyclic amines) during pyrolysis. These types of compounds were detected in traces in the pyrolysates of amino acids, and the finding is very important as the amino acids are components of proteins and are present in food. Some of these compounds isolated from pyrolysates performed at 550 C from several amino acids [5,6] are shown below ... 

Coffee brewed from roasted beans and those prepared from instant powder, including the caffeine-free type, all display mutagenic activity. Apart from natural mutagens such as caffeic acid and its precursors chlorogenic and neochlorogenic acids, these drinks contain mutagenic products of pyrolysis methylglyoxal and less active gly-oxal and diacetyl (Ames, 1986) ... 

These pyrolysis products were also found in roasted tea and brandy-type alcoholic beverages (Sugimura and Sato, 1983). In addition, as a result of ethanol metabolism, mutagenic acetaldehyde is formed, while in coffee and tea caffeine, an inhibitor of DNA repair synthesis is present and may also contribute to cancer risk. 

High-temperature pyrolysis reactions of hydrocarbons are responsible for the production of PAH and solid carbon black particles, soot. This phenomenon is common in diffusion flames where, at high temperatures and without oxygen, hydrocarbon fuel aggregates follow pyrolysis and condensation paths with the formation of heavy aromatic structures. Many PAH s identified in aerosols have been found to be mutagenic and are certainly important soot precursors. This formation of carbonaceous particles has recently become one of the main topics in chemical reaction engineering, especially in the field of pyrolysis and combustion of hydrocarbon fuels. This interest rises from environmental concerns about PAH and soot particle emissions because of their dangerous impact on the human health (Oberdorster et al., 2004). 

Ishikawa, T., Takayama, S., Kitagawa, T., et al., In vivo experiments of trptophan pyrolysis products, in Naturally Occurring Carcinogens-Mutagens and Modulators of Carcinogenesis, Miller, E. C., Miller, I., Hirono, T., et al., Eds., University Park, Baltimore, MD, 1979, 159-167. 

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