Thermally induced process-related contaminants: the example of acrolein and the comparison with acrylamide: opinion of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG)

Elimination of Acrolein by Disodium 5'-Guanylate or Disodium 5'-Inosinate at High Temperature and Its Application in Roasted Pork Patty

Acrolein (ACR) is a highly active, simple unsaturated aldehyde found in various high-temperature processed foods. Its long-term accumulation in the human body increases the risk of chronic diseases. Animal and plant foodstuffs are rich in disodium 5'-guanylate (GMP) and disodium 5'-inosinate (IMP), which are authorized flavor enhancers. Herein, we used liquid chromatography with tandem mass spectrometry to explore the reaction-active kinetics and pathway of the interaction between GMP/IMP and ACR and validated it in roasted pork patties. Our results suggested that GMP and IMP could efficiently eliminate ACR by forming ACR adducts (GMP-ACR, IMP-ACR). In addition, IMP exhibited a higher reaction rate, whereas GMP had a good trapping capacity at a later stage. As carriers of GMP and IMP, dried mushrooms and shrimp exhibited an effective ACR-trapping ability in the ACR model and roasted pork patty individually and in combination. Adding 10% of dried mushroom or shrimp alone or 5% of dried mushroom and shrimp in combination eliminated up to 53.9%, 55.8%, and 55.2% ACR in a roasted pork patty, respectively. This study proposed a novel strategy to eliminate the generation of ACR in roasted pork patties by adding foodstuffs rich in GMP and IMP.

Evaluation of the genotoxic potential of acrylamide: Arguments for the derivation of a tolerable daily intake (TDI value)

This opinion of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) presents arguments for an updated risk assessment of diet-related exposure to acrylamide (AA), based on a critical review of scientific evidence relevant to low dose exposure. The SKLM arrives at the conclusion that as long as an appropriate exposure limit for AA is not exceeded, genotoxic effects resulting in carcinogenicity are unlikely to occur. Based on the totality of the evidence, the SKLM considers it scientifically justified to derive a tolerable daily intake (TDI) as a health-based guidance value.

The role of endogenous versus exogenous sources in the exposome of putative genotoxins and consequences for risk assessment

The “totality” of the human exposure is conceived to encompass life-associated endogenous and exogenous aggregate exposures. Process-related contaminants (PRCs) are not only formed in foods by heat processing, but also occur endogenously in the organism as physiological components of energy metabolism, potentially also generated by the human microbiome. To arrive at a comprehensive risk assessment, it is necessary to understand the contribution of in vivo background occurrence as compared to the ingestion from exogenous sources. Hence, this review provides an overview of the knowledge on the contribution of endogenous exposure to the overall exposure to putative genotoxic food contaminants, namely ethanol, acetaldehyde, formaldehyde, acrylamide, acrolein, α,β-unsaturated alkenals, glycation compounds, N-nitroso compounds, ethylene oxide, furans, 2- and 3-MCPD, and glycidyl esters. The evidence discussed herein allows to conclude that endogenous formation of some contaminants appears to contribute substantially to the exposome. This is of critical importance for risk assessment in the cases where endogenous exposure is suspected to outweigh the exogenous one (e.g. formaldehyde and acrolein).

Adduct Formation of Acrolein with Cyanidin-3-O-glucoside and Its Degradants/Metabolites during Thermal Processing or In Vivo after Consumption of Red Bayberry

Acrolein (ACR) derives from the external environment and the endogenous metabolism of organisms. It has super-reactivity and can induce various diseases. We investigated the capacity of cyanidin-3-O-glucoside (C3G) and its degradants/metabolites to capture ACR during thermal processing or in vivo. Our results indicated that both C3G and its degradants, including phloroglucinaldehyde (PGA) and protocatechuic acid (PCA), could efficiently trap ACR to form adducts, such as C3G-ACR, C3G-2ACR, PGA-ACR, PGA-2ACR, PCA-ACR, and PCA-2ACR. Additionally, these adducts were detected in commercial canned red bayberry products. The adducts of C3G and its metabolites conjugated with ACR, such as C3G-ACR, C3G-2ACR, PGA-ACR, and 4-hydroxybenzoic-acid-ACR (4-HBA-ACR), were also detected in mice feces treated with C3G by oral gavage, where the adduct level was dose-dependent. A similar pattern was observed in tests on human consumption of red bayberry. In human urine, only PGA-2ACR and 4-HBA-ACR, were found, whereas C3G-ACR, C3G-2ACR, myricetin-3-O-rhamnoside-ACR (M3R-ACR), PGA-2ACR, 4-HBA-ACR and ferulic acid-ACR (FA-ACR) were detected in human feces following administration of red bayberry. Our results are the first demonstration that C3G and its metabolites can capture ACR in vitro and in vivo (mice and humans) and present a novel strategy, the development of C3G as a promising ACR inhibitor.

Interconversion and Acrolein-Trapping Capacity of Cardamonin/Alpinetin and Their Metabolites In Vitro and In Vivo

People are at high risk of exposure to endogenous and exogenous acrolein (ACR). ACR can cause a multitude of illnesses, including cardiovascular disease, Alzheimer's disease, and diabetes. In this study, we investigated the reaction pathway of cardamonin (CAR) or alpinetin (ALP) with ACR and the interconversion of CAR and ALP in vitro at 37 °C in phosphate-buffered saline using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Subsequently, ACR adducts of CAR, ALP, and their metabolites, for example, CAR-ACR-1, ALP-ACR, mono-ACR-pinocembrin chalcone (PIN-ACR), and mono- and di-ACR-naringenin (NAR-ACR and NAR-2ACR), were detected in urine samples, but only CAR-ACR-1 and ALP-ACR were detected in fecal samples from the CAR- and ALP-treated mouse groups using ultraperformance liquid chromatography-MS/MS, respectively. Quantitative analyses showed that CAR, ALP, and their metabolites markedly scavenged ACR in a dose-dependent manner in vivo. Furthermore, we also found that the metabolites of CAR or ALP remained and promoted the ACR-trapping ability.

Trapping Acrolein by Theophylline/Caffeine and Their Metabolites from Green Tea and Coffee in Mice and Humans

Acrolein (ACR) is found exogenously as a widespread environmental pollutant and endogenously, where it is thought to be involved as a pathogenic factor in the progression of many pathological conditions. Eliminating ACR by dietary-active substances has been found to be one potential strategy to prevent ACR-associated chronic diseases. This study first compared the scavenging ACR efficacy of four purine alkaloids, theophylline (TP), paraxanthine (PXT), theobromine (TB), and caffeine (CAF), and then, TP, CAF, and their metabolites were investigated for their ability to trap ACR in vivo. Our results indicated that TP, which possesses an -NH moiety at the N-7 position, exhibits the best ACR-trapping capacity in vitro, while CAF has a slight ability to trap ACR due to the substitutions by -CH₃ at the N-1, N-3, and N-7 positions. After oral administration of TP or CAF, the ACR adducts of TP and the metabolites of TP or CAF (e.g., mono- and di-ACR-TP, mono-ACR-1,3-DMU, and mono-ACR-1-MU) were detected in urinary samples obtained from both TP- and CAF-treated mouse groups by using ultra-performance liquid chromatography-tandem mass spectrometry. The quantification studies demonstrated that TP and its metabolites significantly trapped ACR in a dose-dependent manner in vivo. Furthermore, we also detected those ACR adducts of TP and TP/CAF's metabolites in human urine after four cups of green tea (2 g tea leaf/cup) or two cups of coffee (4 g coffee/cup) were consumed per day. Those results indicated that dietary TP or CAF has the potential capacity to scavenge ACR in vivo.

Mode of action-based risk assessment of genotoxic carcinogens

The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.

Exposure assessment of process-related contaminants in food by biomarker monitoring

Exposure assessment is a fundamental part of the risk assessment paradigm, but can often present a number of challenges and uncertainties. This is especially the case for process contaminants formed during the processing, e.g. heating of food, since they are in part highly reactive and/or volatile, thus making exposure assessment by analysing contents in food unreliable. New approaches are therefore required to accurately assess consumer exposure and thus better inform the risk assessment. Such novel approaches may include the use of biomarkers, physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry, and/or duplicate diet studies. This review focuses on the state of the art with respect to the use of biomarkers of exposure for the process contaminants acrylamide, 3-MCPD esters, glycidyl esters, furan and acrolein. From the overview presented, it becomes clear that the field of assessing human exposure to process-related contaminants in food by biomarker monitoring is promising and strongly developing. The current state of the art as well as the existing data gaps and challenges for the future were defined. They include (1) using PBK modelling and duplicate diet studies to establish, preferably in humans, correlations between external exposure and biomarkers; (2) elucidation of the possible endogenous formation of the process-related contaminants and the resulting biomarker levels; (3) the influence of inter-individual variations and how to include that in the biomarker-based exposure predictions; (4) the correction for confounding factors; (5) the value of the different biomarkers in relation to exposure scenario's and risk assessment, and (6) the possibilities of novel methodologies. In spite of these challenges it can be concluded that biomarker-based exposure assessment provides a unique opportunity to more accurately assess consumer exposure to process-related contaminants in food and thus to better inform risk assessment.

Acrolein contributes strongly to antimicrobial and heterocyclic amine transformation activities of reuterin

Glycerol/diol dehydratases catalyze the conversion of glycerol to 3-hydroxypropionaldehyde (3-HPA), the basis of a multi-component system called reuterin. Reuterin has antimicrobial properties and undergoes chemical conjugation with dietary heterocyclic amines (HCAs). In aqueous solution reuterin is in dynamic equilibrium with the toxicant acrolein. It was the aim of this study to investigate the extent of acrolein formation at various physiological conditions and to determine its role in biological and chemical activities. The application of a combined novel analytical approach including IC-PAD, LC-MS and NMR together with specific acrolein scavengers suggested for the first time that acrolein, and not 3-HPA, is the active compound responsible for HCA conjugation and antimicrobial activity attributed to reuterin. As formation of the HCA conjugate was observed in vivo, our results imply that acrolein is formed in the human gut with implications on detoxification of HCAs. We propose to re-define the term reuterin to include acrolein.

An integrated QSAR-PBK/D modelling approach for predicting detoxification and DNA adduct formation of 18 acyclic food-borne α,β-unsaturated aldehydes

Acyclic α,β-unsaturated aldehydes present in food raise a concern because the α,β-unsaturated aldehyde moiety is considered a structural alert for genotoxicity. However, controversy remains on whether in vivo at realistic dietary exposure DNA adduct formation is significant. The aim of the present study was to develop physiologically based kinetic/dynamic (PBK/D) models to examine dose-dependent detoxification and DNA adduct formation of a group of 18 food-borne acyclic α,β-unsaturated aldehydes without 2- or 3-alkylation, and with no more than one conjugated double bond. Parameters for the PBK/D models were obtained using quantitative structure-activity relationships (QSARs) defined with a training set of six selected aldehydes. Using the QSARs, PBK/D models for the other 12 aldehydes were defined. Results revealed that DNA adduct formation in the liver increases with decreasing bulkiness of the molecule especially due to less efficient detoxification. 2-Propenal (acrolein) was identified to induce the highest DNA adduct levels. At realistic dietary intake, the predicted DNA adduct levels for all aldehydes were two orders of magnitude lower than endogenous background levels observed in disease free human liver, suggesting that for all 18 aldehydes DNA adduct formation is negligible at the relevant levels of dietary intake. The present study provides a proof of principle for the use of QSAR-based PBK/D modelling to facilitate group evaluations and read-across in risk assessment.