Analysis of cooked muscle meats for heterocyclic aromatic amine carcinogens

Heterocyclic aromatic amines in meat: Formation mechanisms, toxicological implications, occurrence, risk evaluation, and analytical methods

Heterocyclic aromatic amines (HAAs) are detrimental substances can develop during the high-temperature cooking of protein-rich foods, such as meat. They are potent mutagens and carcinogens linked to an increased risk of various cancers. HAAs have complex structures with nitrogen-containing aromatic rings and are formed through chemical reactions between amino acids, creatin(in)e, and sugars during cooking. The formation of HAAs is influenced by various factors, such as food type, cooking temperature, time, cooking method, and technique. HAAs exert their toxicity through mechanisms like DNA adduct formation, oxidative stress, and inflammation. The research on HAAs is important for public health and food safety, leading to risk assessment and management strategies. It has also led to innovative approaches for reducing HAAs formation during cooking and minimizing related health risks. Understanding HAAs' chemistry and formation is crucial for developing effective ways to prevent their occurrence and protect human health. The current review presents an overview about HAAs, their formation pathways, and the factors influencing their formation. Additionally, it reviews their adverse health effects, occurrence, and the analytical methods used for measuring them.

The Effects of the Marination Process with Different Vinegar Varieties on Various Quality Criteria and Heterocyclic Aromatic Amine Formation in Beef Steak

Herein, the effect of the dipping (static) marination process (at 4 °C for 2 h) with different types of vinegar (balsamic, pomegranate, apple, and grape) on various quality properties, including texture and protein profile of beef steaks and the formation of heterocyclic aromatic amines (HAAs) in beef steaks cooked on a hot plate (at 200 °C for 24 min), were determined. The results showed that 3.12–4.13% of the marinate liquids were absorbed by beef steak as a result of the marination process. No significant differences (p > 0.05) were observed between the marinated and cooked beef steaks in terms of water content, cooking loss, thiobarbituric acid reactive substances (TBARS) value, hardness, cohesiveness, and chewiness. However, significant differences were detected in terms of pH value and color values (L*, a*, and b*) (p < 0.01), and springiness, 2-amino-3,8-dimethylimidazo (4,5-f) quinoxaline (MeIQx) and total HAA content (p < 0.05). The marination with pomegranate vinegar resulted in the formation of darker steak, while a lighter one was obtained when apple vinegar was used in the marination. The use of balsamic and grape vinegar in the marination process decreased the springiness value compared to the control group. The myofibrillar proteins of beef steaks marinated with different types of vinegar generally showed a similar sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile. However, some differences were observed in the band density of some proteins depending on the trial and the type of marination. In this study, of the nine examined HAAs, only two (2-amino-3-methylimidazo (4,5-f) quinoline (IQ) and MeIQx) could be detected and quantified. IQ was detected only in the control group steak (up to 0.51 ng/g), while MeIQx was detected in all treatment groups (up to 2.22 ng/g). The total HAA content varied between 0.59–2.22 ng/g. It was determined that the marination process with different vinegar types had different effects on the total HAA content of the steaks. Using balsamic and apple vinegar in the marination process decreased the total HAA content compared to the control group, but this decrease was not statistically significant (p > 0.05). On the other hand, using grape and pomegranate vinegar in the marination process increased the total HAA content, but this increase was only significant (p < 0.05) in the marination with pomegranate vinegar.

Health inequity drives disease biology to create disparities in prostate cancer outcomes

Prostate cancer exerts a greater toll on African American men than on White men of European descent (hereafter referred to as European American men): the disparity in incidence and mortality is greater than that of any other common cancer. The disproportionate impact of prostate cancer on Black men has been attributed to the genetics of African ancestry, to diet and lifestyle risk factors, and to unequal access to quality health care. In this Review, all of these influences are considered in the context of the evolving understanding that chronic or recurrent inflammatory processes drive prostatic carcinogenesis. Studies of inherited susceptibility highlight the contributions of genes involved in prostate cell and tissue repair (BRCA1/2, ATM) and regeneration (HOXB13 and MYC). Social determinants of health appear to accentuate these genetic influences by fueling prostate inflammation and associated cell and genome damage. Molecular characterization of the prostate cancers that arise in Black versus White men further implicates this inflammatory microenvironment in disease behavior. Yet, when Black and White men with similar grade and stage of prostate cancer are treated equally, they exhibit equivalent outcomes. The central role of prostate inflammation in prostate cancer development and progression augments the impact of the social determinants of health on disease pathogenesis. And, when coupled with poorer access to high-quality treatment, these inequities result in a disparate burden of prostate cancer on African American men.

Chemical hazards in smoked meat and fish

This review aims to give an insight into the main hazards currently found in smoked meat and fish products. Literature research was carried out on international databases such as Access to Global Online Research in Agriculture (AGORA) database, Science direct, and Google scholar to collect and select 92 relevant publications included in this review. The smoking process was described and five hazards mostly found in smoked fish and meat were presented. The heat-induced compounds such as polycyclic aromatic hydrocarbons, heterocyclic amines, and nitrosamines were found in smoked fish and meat. Other hazards such as biogenic amines and heavy metals were also present in smoked fish and meat. The levels of these hazards reported from the literature exceeded the maximal limits of European Union. A brief description of risk assessment methodology applicable to such toxic compounds and risk assessment examples was also presented in this review. As most of the hazards reported in this review are toxic and even carcinogenic to humans, actions should be addressed to reduce their presence in food to protect consumer health and to prevent public health issue.

Heterocyclic Aromatic Amines in Meat: Formation, Isolation, Risk Assessment, and Inhibitory Effect of Plant Extracts

Heterocyclic aromatic amines (HAAs) are potent carcinogenic compounds induced by the Maillard reaction in well-done cooked meats. Free amino acids, protein, creatinine, reducing sugars and nucleosides are major precursors involved in the production of polar and non-polar HAAs. The variety and yield of HAAs are linked with various factors such as meat type, heating time and temperature, cooking method and equipment, fresh meat storage time, raw material and additives, precursor’s presence, water activity, and pH level. For the isolation and identification of HAAs, advanced chromatography and spectroscopy techniques have been employed. These potent mutagens are the etiology of several types of human cancers at the ng/g level and are 100- to 2000-fold stronger than that of aflatoxins and benzopyrene, respectively. This review summarizes previous studies on the formation and types of potent mutagenic and/or carcinogenic HAAs in cooked meats. Furthermore, occurrence, risk assessment, and factors affecting HAA formation are discussed in detail. Additionally, sample extraction procedure and quantification techniques to determine these compounds are analyzed and described. Finally, an overview is presented on the promising strategy to mitigate the risk of HAAs by natural compounds and the effect of plant extracts containing antioxidants to reduce or inhibit the formation of these carcinogenic substances in cooked meats.

Analysis of Heterocyclic Amines in Meat by the Quick, Easy, Cheap, Effective, Rugged, and Safe Method Coupled with LC-DAD-MS-MS

The traditional way to analyze heterocyclic amines (HAs) is time-consuming and uses large amounts of solvents. The objective of this study is to develop a quick and simultaneous analysis method for multiple types of HAs contained in meat products. Results showed that 20 HAs and 1 internal standard (4,7,8-TriMeIQx) can be separated within 30 min using an Inspire C18 column and a gradient solvent system containing 10 mM ammonium acetate (pH 2.9) and acetonitrile. This process resulted in a high degree of separation. Using acetonitrile with 1% acetic acid as an extraction solvent, followed by primary and secondary amine, MgSO₄, and C18EC as purified reagent, is highly suitable for extracting HAs using the quick, easy, cheap, effective, rugged, and safe method (QuEChERS). Tandem mass spectrometry with selected reaction monitoring mode were used for analysis, which indicated reasonable recovery (58.9-117.4%) for all 20 types of HAs along with limits of detection and quantification in the range of 0.003-0.05 and 0.01-0.05 ng/g, respectively.

Heterocyclic Aromatic Amines in Cooked Meat Products: Causes, Formation, Occurrence, and Risk Assessment

Meat products are sources of protein with high biological value and an essential source of other nutrients, such as vitamins and minerals. Heating processes cause food to become more appetizing with changes in texture, appearance, flavor, and chemical properties by the altering of protein structure and other ingredients. During heat treatment, heterocyclic aromatic amines (HAAs), potent mutagens/carcinogens, are formed due to the Maillard reaction. The HAAs are classified in at least 2 groups: thermic HAAs (100 to 300 °C) and pyrolytic HAAs (>300 °C). This review focuses on the parameters and precursors which affect the formation of HAAs: preparation, such as the marinating of meat, and cooking methods, including temperature, duration, and heat transfer, as well as levels of precursors. Additionally, factors are described subject to pH, and the type of meat and ingredients, such as added antioxidants, types of carbohydrates and amino acids, ions, fat, and other substances inhibiting or enhancing the formation of HAAs. An overview of the different analytical methods available is shown to determine the HAAs, including their preparation to clean up the sample prior to extraction. Epidemiological results and human daily intake of HAAs obtained from questionnaires show a relationship between the preference for very well-done meat products with increased HAA levels and an enhanced risk of the incidence of cancer, besides other carcinogens in the diet. The metabolic pathway of HAAs is governed by the activity of several enzymes leading to the formation of DNA adducts or HAA excretion and genetic sensitivity of individuals to the impact of HAAs on human cancer risk.

Molecular Updates in Prostate Cancer

A wide array of molecular markers and genomic signatures, reviewed in this article, may soon be used as adjuncts to currently established screening strategies, prognostic parameters, and early detection markers. Markers of genetic susceptibility to PCA, recurrent epigenetic and genetic alterations, including ETS gene fusions, PTEN alterations, and urine-based early detection marker PCA3, are discussed. Impact of recent genome-wide assessment on our understanding of key pathways of PCA development and progression and their potential clinical implications are highlighted.

The diet as a cause of human prostate cancer

Asymptomatic prostate inflammation and prostate cancer have reached epidemic proportions among men in the developed world. Animal model studies implicate dietary carcinogens, such as the heterocyclic amines from over-cooked meats and sex steroid hormones, particularly estrogens, as candidate etiologies for prostate cancer. Each acts by causing epithelial cell damage, triggering an inflammatory response that can evolve into a chronic or recurrent condition. This milieu appears to spawn proliferative inflammatory atrophy (PIA) lesions, a type of focal atrophy that represents the earliest of prostate cancer precursor lesions. Rare PIA lesions contain cells which exhibit high c-Myc expression, shortened telomere segments, and epigenetic silencing of genes such as GSTP1, encoding the π-class glutathione S-transferase, all characteristic of prostatic intraepithelial neoplasia (PIN) and prostate cancer. Subsequent genetic changes, such as the gene translocations/deletions that generate fusion transcripts between androgen-regulated genes (such as TMPRSS2) and genes encoding ETS family transcription factors (such as ERG1), arise in PIN lesions and may promote invasiveness characteristic of prostatic adenocarcinoma cells. Lethal prostate cancers contain markedly corrupted genomes and epigenomes. Epigenetic silencing, which seems to arise in response to the inflamed microenvironment generated by dietary carcinogens and/or estrogens as part of an epigenetic "catastrophe" affecting hundreds of genes, persists to drive clonal evolution through metastatic dissemination. The cause of the initial epigenetic "catastrophe" has not been determined but likely involves defective chromatin structure maintenance by over-exuberant DNA methylation or histone modification. With dietary carcinogens and estrogens driving pro-carcinogenic inflammation in the developed world, it is tempting to speculate that dietary components associated with decreased prostate cancer risk, such as intake of fruits and vegetables, especially tomatoes and crucifers, might act to attenuate the ravages of the chronic or recurrent inflammatory processes. Specifically, nutritional agents might prevent PIA lesions or reduce the propensity of PIA lesions to suffer "catastrophic" epigenome corruption.

Dietary Chlorella protects against heterocyclic amine-induced aberrant gene expression in the rat colon by increasing fecal excretion of unmetabolized PhIP

The food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the most abundant heterocyclic amines formed by cooking meat and fish at high temperature. PhIP induces colorectal adenoma risk in male rats when administered orally. This study used male Fisher 344 rats to investigate the impact of dietary Chlorella on PhIP metabolism and aberrant colonic gene expression following short-term PhIP treatment. High-performance liquid chromatography analysis revealed that fecal excretion of unmetabolized PhIP was significantly increased in rats whose diets were supplemented with Chlorella compared to rats in a PhIP-only group (P<0.001). Quantitative realtime PCR confirmed that the increase in beta-catenin and cyclin D1 mRNA in the colon induced by PhIP was ameliorated in rats pre-fed with Chlorella (P=0.052 for beta-catenin; P=0.005 for cyclin D1). The increase in DNA shearing that is a hallmark of caspase-8-mediated apoptosis by PhIP was also significantly diminished in the colons of rats pre-fed Chlorella (P=0.012). These results suggested that administering dietary Chlorella with a Western-style diet concomitantly or immediately before mutagen exposure might be beneficial in blocking the absorption of food mutagens such as PhIP.

Detection of PhIP in grilled chicken entrées at popular chain restaurants throughout California

Heterocyclic amines (HCAs), compounds formed when meat is cooked at high temperatures particularly through pan frying, grilling, or barbequing, pose a potential carcinogenic risk to the public. It is unclear whether there is any level at which consumption of HCAs can be considered safe. Efforts to measure these compounds mainly include cooking studies under laboratory conditions and some measurement of home-cooked foods, but analysis of commercially cooked foods has been minimal. Attempts to estimate exposure of the public to these compounds must take into consideration dining outside the home, which could result in significant exposure for some individuals. We surveyed at least 9 locations each of 7 popular chain restaurants (McDonald's, Burger King, Chick-fil-A, Chili's, TGI Friday's, Outback Steakhouse, and Applebee's) in California, collecting one or two entrees from each location. Entrees were analyzed for 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using high-performance liquid chromatography tandem mass spectrometry. All 100 samples contained PhIP. Concentrations were variable within and between entrees and ranged from 0.08 to 43.2 ng/g. When factoring in the weight of the entrees, absolute levels of PhIP reached over 1,000 ng for some entrees. Potential strategies for reducing exposure include the avoidance of meats cooked using methods that are known to form PhIP.

Validity of a self-administered food frequency questionnaire in the assessment of heterocyclic amine intake using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) levels in hair

Several case-control studies have reported possible associations between heterocyclic amine (HCA) intake and the risk of cancer. The validity of questionnaires used to assess HCA intake has hardly been examined, however; in particular, no biomarker able to serve as an independent measure of habitual HCA intake has been established. In this study, we examined the validity of HCA intake estimated from a food frequency questionnaire (FFQ) using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) level in hair as a reference method. Study subjects were 20 volunteers (7 men and 13 women) aged 25-57 years residing in Tokyo or neighboring cities in Japan. The subjects completed the FFQ, and gave 3-5g of hair twice at an interval of 1-3 months for use in establishing validity. Results showed that intakes of PhIP, MeIQ, Trp-P-1, and total HCA by the FFQ were significantly correlated with PhIP levels in hair when adjustment was made for melanin content (r=0.47, r=0.50, r=0.55, and r=0.51, respectively). The present study indicates that HCA intake estimated from this FFQ provides a reasonable ranking of individuals to allow the analysis of associations between HCA intake and risk of cancer in large-scale epidemiological studies.

Dietary exposure to heterocyclic amines in a Chinese population

Heterocyclic aromatic amines (HAAs) formed in meat during high-temperature cooking have been associated with risk of colorectal and breast cancer. Incidence of these cancers is increasing in Singapore, a country with 77% ethnic Chinese. The purpose of this study was to estimate HAA levels in the Chinese diet and individual levels of exposure to these compounds because little is known. Twenty-five samples (each pooled from three sources) of meat and fish, cooked as commonly consumed, were analyzed by high-performance liquid chromatography for concentrations (ng/g) of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3, 4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8- dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3, 4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2- amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline, 2-amino -1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine, and 2- amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Dietary meat consumption data (g/day), including meat type and cooking method, were gathered from food-frequency questionnaires completed by 497 randomly sampled Chinese men and women aged 20-59 yr. PhIP, MeIQx, and 4,8-DiMeIQx were the most abundant HAAs detected. Total HAA concentrations ranged from <0.10 to 6.77 ng/g, of which Chinese-style roasted pork had the highest levels. The estimated mean daily exposure to HAA was 49.95 ng/day (P10 14.0 ng/day, P90 95.8 ng/day); this was 50% higher among younger (20-39 yr) compared with older individuals. Seven specific meat-cooking method combinations contributed 90.1% of this intake, namely, pan-fried fish, pork, and chicken, deep-fried chicken as well as fish, roasted/barbecued pork, and grilled minced beef.

GSTP1 CpG island hypermethylation as a molecular biomarker for prostate cancer

Somatic hypermethylation of CpG island sequences at GSTP1, the gene encoding the pi-class glutathione S-transferase, appears to be characteristic of human prostatic carcinogenesis. To consider the potential utility of this epigenetic alteration as a biomarker for prostate cancer, we present here a comprehensive review of the literature describing somatic GSTP1 changes in DNA from prostate cells and tissues. GSTP1 CpG island hypermethylation has been detected in prostate cancer DNA using a variety of assay techniques, including (i) Southern blot analysis (SB), after treatment with (5-m)C-sensitive restriction endonucleases, (ii) the polymerase chain reaction, following treatment with (5-m)C-sensitive restriction endonucleases (RE-PCR), (iii) bisulfite genomic sequencing (BGS), and (iv) bisulfite modification followed by the polymerase chain reaction, using primers selective for target sequences containing (5-m)C (MSP). In the majority of the case series so far reported, GSTP1 CpG island hypermethylation was present in DNA from at least 90% of prostate cancer cases. When analyses have been carefully conducted, GSTP1 CpG island hypermethylation has not been found in DNA from normal prostate tissues, or from benign prostatic hyperplasia (BPH) tissues, though GSTP1 CpG island hypermethylation changes have been detected in DNA from candidate prostate cancer precursor lesions proliferative inflammatory atrophy (PIA) and prostatic intraepithelial neoplasia (PIN). Using PCR methods, GSTP1 CpG island hypermethylation has also been detected in urine, ejaculate, and plasma from men with prostate cancer. GSTP1 CpG island hypermethylation, a somatic epigenetic alteration, appears poised to serve as a molecular biomarker useful for prostate cancer screening, detection, and diagnosis.

Pathological and molecular mechanisms of prostate carcinogenesis: implications for diagnosis, detection, prevention, and treatment

Prostate cancer is an increasing threat throughout the world. As a result of a demographic shift in population, the number of men at risk for developing prostate cancer is growing rapidly. For 2002, an estimated 189,000 prostate cancer cases were diagnosed in the U.S., accompanied by an estimated 30,200 prostate cancer deaths [Jemal et al., 2002]. Most prostate cancer is now diagnosed in men who were biopsied as a result of an elevated serum PSA (>4 ng/ml) level detected following routine screening. Autopsy studies [Breslow et al., 1977; Yatani et al., 1982; Sakr et al., 1993], and the recent results of the Prostate Cancer Prevention Trial (PCPT) [Thompson et al., 2003], a large scale clinical trial where all men entered the trial without an elevated PSA (<3 ng/ml) were subsequently biopsied, indicate the prevalence of histologic prostate cancer is much higher than anticipated by PSA screening. Environmental factors, such as diet and lifestyle, have long been recognized contributors to the development of prostate cancer. Recent studies of the molecular alterations in prostate cancer cells have begun to provide clues as to how prostate cancer may arise and progress. For example, while inflammation in the prostate has been suggested previously as a contributor to prostate cancer development [Gardner and Bennett, 1992; Platz, 1998; De Marzo et al., 1999; Nelson et al., 2003], research regarding the genetic and pathological aspects of prostate inflammation has only recently begun to receive attention. Here, we review the subject of inflammation and prostate cancer as part of a "chronic epithelial injury" hypothesis of prostate carcinogenesis, and the somatic genome and phenotypic changes characteristic of prostate cancer cells. We also present the implications of these changes for prostate cancer diagnosis, detection, prevention, and treatment.

Mammary gland carcinogenesis by food-derived heterocyclic amines and studies on the mechanisms of carcinogenesis of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)

The heterocyclic amines (HCAs) comprise a family of mutagenic/carcinogenic compounds found in cooked meat. Several HCAs including 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are mammary gland carcinogens in rats. One mammary gland carcinogen, PhIP, is the most prevalent in the human diet. This article reviews the mechanisms of mammary gland carcinogenesis of PhIP including metabolic processing, DNA adduct formation, effects on mammary gland development, cell signaling, and the genomic alterations found in PhIP-induced rat mammary gland carcinomas.

Biomarkers of exposure to heterocyclic amines: approaches to improve the exposure assessment

Various methods of exposure assessment, such as questionnaires, sometimes combined with pictures of cooked meat, have been employed in investigations on the relationship between heterocyclic amines (HA) and health effects. However, as the content of heterocyclic amines vary greatly with cooking conditions, it is difficult to obtain an accurate estimate of the exposure. To improve the exposure assessment, the use of biomarkers has been investigated. The metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is well characterised. In humans, the major part of the dose is excreted in urine within 24-48 h following a meal. A few percent is excreted as parent compounds, whereas the major part is metabolites. Urinary level of parent HA reflects only recent exposure. However, the pattern of excreted metabolites might indicate the capacity to activate or detoxify HAs. The excretion of glucuronide conjugates of N-hydroxy-PhIP and N-hydroxy-MeIQx could be a marker for the N-hydroxylation capacity and the dose of the proximate metabolites. Recently, we proposed 5-OH-PhIP as a marker for the ultimate reactive metabolite of PhIP, since it is formed from this compound as a by-product along with the formation of PhIP-DNA adducts. In a search for biomarkers reflecting exposure over some time, blood protein adducts with a longer lifespan have been investigated, and PhIP adducts of serum albumin and haemoglobin from meat-consuming humans were recently reported. Many compounds, like drugs, nicotine and narcotics, bind to melanin in hair and give information on exposure for longer time periods. In mice, PhIP is irreversibly incorporated in a dose-dependent manner into hair, and in humans exposed to an ordinary diet, it was found to vary from <50 to 5000 pg PhIP/g hair. The incorporation is also dependent on the content of eumelanin. The use of PhIP in hair as a biomarker of exposure is promising, but needs validation, using other methods of exposure assessment.

Green tea and the metabolism of 2-amino-3-methylimidazo

The effects of green tea intake on the metabolism of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the rat was studied. IQ belongs to a new class of mutagens and carcinogens, heterocyclic arylamines, formed during cooking through browning meats and fish, thus, in the food chain of most non-vegetarians. Ten adult male and female Fischer 344 rats were placed on a 2% solution of green tea and 10 control rats were on water for 6 weeks. Then, animals were administered a single dose of 40 mg/kg body weight of [2-14C]IQ by oral gavage. Twenty-four hour urine samples were collected and metabolites were separated by HPLC and quantitated by scintillation counting. Two minor and three major metabolites were isolated, including, small quantities of IQ itself. The rats on tea showed significant differences (P < 0.05) in the recovery of the three major metabolites, namely, IQ-sulfamate, IQ-5-O-sulfate, and IQ-5-O-glucuronide, respectively. Green tea, therefore, influences the manner in which the food carcinogen IQ is metabolized and excreted in urine. Formation of glucuronides, increased by green tea, represent a key means of detoxification of the heterocyclic amine, IQ.

Separation of heteroaromatic amines in food products

In recent years, many studies have dealt with the role of certain heteroaromatic amines (HAs) as mutagenic compounds, and their occurrence in foodstuffs. Here we examine the determination of HAs, focusing on the analytical strategies for their extraction and preconcentration from several matrices. We summarise the properties of heteroaromatic amines and the main drawbacks involved in their analysis, and then concentrate on the separation procedures, sorbents and solvents used in the sample treatment. We discuss the requirements of the analytical techniques and the strategies most frequently followed to achieve accurate results.

Quantitative structure-activity relationship of flavonoids for inhibition of heterocyclic amine mutagenicity

The mutagenic/carcinogenic heterocyclic amines formed during the cooking of protein foods have been determined to be a potential risk to human health. Therefore, mitigation measures are beginning to be studied. A recent finding is that the induction of mutation in Salmonella by these amines can be inhibited by the addition of flavonoids to the assay. This study combines data on the inhibitory process with structural, ab initio quantum chemical, hydropathic, and antioxidant factors to develop a quantitative structure-activity relationship (QSAR) database and statistical analysis. For 39 diverse flavonoids the inhibitory potency varied approximately 100-fold. Three predictive variables, in order of decreasing contribution to variance, are: (1) a large dipole moment; (2) after geometric minimization of energy, a small departure from planarity (i.e., small dihedral angle between the benzopyran nucleus and the attached phenyl ring), and a low rotational energy barrier to achieving planarity; and (3) fewer hydroxyl groups on the phenyl ring. However, these variables account for less than half of the variance in inhibitory potency of the flavonoids. Frontier orbital energies and antioxidant or radical scavenging properties showed little or no relationship to potency. We conclude that interference by the flavonoids with cytochrome P450 activation of the promutagens is the probable mechanism for inhibition of mutagenesis, and suggest avenues for further research. Environ. Mol. Mutagen. 35:279-299, 2000 Published 2000 Wiley-Liss, Inc.

Factors determining dietary intakes of heterocyclic amines in cooked foods

The identification of heterocyclic amines (HCAs) in cooked foods has focused attention on the potential health effects from their consumption in the diet. Recent studies have estimated daily dietary intakes of HCAs that vary 10-fold and implicated different cooked meats as the prime source of HCAs in the diet. These varied estimates can be attributed to the different dietary assessment methods used in these studies, as well as the different levels of HCAs ascribed to the most commonly consumed cooked meats. Epidemiological studies utilizing information on dietary practice and food intake have found higher risks for several cancers among individuals consuming the highest levels of HCAs. These studies have highlighted the importance of using information on cooking methods in addition to food intake to accurately estimate dietary exposure to HCAs.

Heterocyclic amines in process flavours, process flavour ingredients, bouillon concentrates and a pan residue

Seven process flavours, five process flavour ingredients, four bouillon concentrates and a pan residue were analysed for mutagenic/carcinogenic heterocyclic amines. To improve chromatographic efficiency for samples with complex matrixes (process flavours, pan residues, etc.), a new additional purification method was designed. The following polar heterocyclic amines were detected: 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in one sample (3.4 ng/g), 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQx) in two samples (0.7-2.0 ng/g), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in four samples (1.0-13.8 ng/g), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) in three samples (1.3-2.9 ng/g), 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx) in one sample (0.3 ng/g), and traces of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in two samples. 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) was not identified in any of the samples. The following non-polar heterocyclic amines were detected: 2-amino-9H-pyrido[2,3-b]indole (AalphaC) in one sample (0.4 ng/g), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) in one sample (20.3 ng/g), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) in two samples (1.4-1.7 ng/g), and traces of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in two samples. Of the co-mutagenic heterocyclic amines, 1-methyl-9H-pyrido[3,4-b]indole (harman) was identified in 15 of 17 samples (3.3-755 ng/g), and 9H-pyrido[3,4-b]indole (norharman) in 16 of 17 samples (1.2-176 ng/g). The polar heterocyclic amines were detected only in the samples of animal and mixed animal plus vegetable origin, while the non-polar heterocyclic amines were identified in samples of animal, mixed animal plus vegetable and pure vegetable origin.

Carcinogenic heterocyclic amines in model systems and cooked foods: a review on formation, occurrence and intake

Frying or grilling of meat and fish products may generate low ppb levels of mutagenic/carcinogenic heterocyclic amines (HAs). Many heterocyclic amines are formed via the Maillard reaction from creatine, free amino acids and monosaccharides; compounds naturally occurring in protein-rich foods of animal origin. The formation and yield of HAs are dependent on physical parameters, such as cooking temperature and time, cooking technique and equipment, heat and mass transport, and on chemical parameters, especially the precursors to HAs. This paper reviews the current knowledge on the formation of HAs in cooked foods and model systems, and summarizes data on the content of HAs in various cooked foods, and estimates of the dietary intake of HAs. It should be noted that the presence of carcinogens of other types in food (e.g. nitrosamines, aromatic amines, cholesterol oxide products) and that their generation during frying and grilling are outside the scope of this review.