Formation,determination and significance of masked and other conjugated mycotoxins

Mycotoxins are secondary metabolites of fungi poisonous for humans or animals which can be found on a great variety of food and feed commodities. Food is not necessarily safe just because the presence of well-known mycotoxins has been ruled out, as they might still be there in disguise. Mycotoxins may also occur in conjugated form, either soluble (masked mycotoxins) or incorporated into/associated with/attached to macromolecules (bound mycotoxins). These conjugated mycotoxins can emerge after metabolization by living plants, fungi and mammals or after food processing. Awareness of such altered forms of mycotoxins is increasing, but reliable analytical methods, measurement standards and occurrence and toxicity data are still lacking. In this paper currently known conjugated mycotoxins, their formation and determination are reviewed. For the latter, liquid chromatography-(tandem) mass spectrometry or ELISA methods are employed with or without conversion to the parent mycotoxins. Sample preparation to transform the bound forms into soluble forms can involve enzymatic or acidic/alkaline treatment. Especially mycotoxins which are in contact with living plants in the field are prone to be metabolized. This transformation process is not only important regarding food safety but also for the resistance of plants towards fungal-induced diseases, such as Fusarium head blight of wheat.     

Determination of mycotoxins in human foods

This tutorial review deals with the analytical methods available for the determination of mycotoxins in food commodities. As the secondary metabolites of a range of fungal species, mycotoxins possess diverse chemical structures, presenting analytical chemists with a unique set of challenges in the microg kg(-1) (ppb) range. A number of analytical methods have been applied to mycotoxin analysis. These include widely applicable HPLC methods with UV or fluorimetric detection, which are extensively used both in research and for legal enforcement of food safety legislation and for regulations in international agricultural trade. Other chromatographic methods, such as TLC and GC, are also employed for the determination of mycotoxins, whereas recent advances in analytical instrumentation have highlighted the potential of LC-MS methods, especially for multi-toxin determination and for confirmation purposes. Conventional chromatographic methods are generally time consuming and capital intensive, and hence a range of methods, mostly based on immunological principles, have been developed and commercialised for rapid analysis. These methods include, among others, enzyme-linked immunosorbent analysis (ELISA), direct fluorimetry, fluorescence polarization, and various biosensors and strip methods.     

Analytical methods for determination of mycotoxins: An update (2009–2014)

Mycotoxins are a problematic and toxic group of small organic molecules that are produced as secondary metabolites by several fungal species that colonise crops. They lead to contamination at both the field and postharvest stages of food production with a considerable range of foodstuffs affected, from coffee and cereals, to dried fruit and spices. With wide ranging structural diversity of mycotoxins, severe toxic effects caused by these molecules and their high chemical stability the requirement for robust and effective detection methods is clear.     

Recent Advances in Electrochemical Sensors for Mycotoxin Detection in Food

Mycotoxins pose a grave global threat to human life and health by contaminating food and feed and cause enormous losses in healthcare and trading. Trace mycotoxin concentrations and diverse matrices in food make identification and measurement challenges, necessitating highly specific and sensitive detection methods. Electrochemical (EC) sensors are characterized by simple operation, outstanding sensitivity, low cost, and facile miniaturization and have become a promising strategy for addressing specificity and sensitivity in detection. Recent studies on EC sensors for mycotoxin detection for food safety are reviewed here. First, we summarize the fabrication of EC sensors and techniques with enhanced specificity and sensitivity. Then, we review state-of-the-art EC sensors for detecting major mycotoxins. Challenges and opportunities for this technology are further discussed. Finally, in-depth information is provided on using EC sensors to detect mycotoxins for food safety, as well as the development of EC sensors for academic study and practical application.     

Trace mycotoxin analysis in complex biological and food matrices by liquid chromatography-atmospheric pressure ionisation mass spectrometry

Mycotoxins are toxic secondary metabolites produced by filamentous fungi that are growing on agricultural commodities. Their frequent presence in food and their severe toxic, carcinogenic and estrogenic properties have been recognised as potential threat to human health. A reliable risk assessment of mycotoxin contamination for humans and animals relies basically on their unambiguous identification and accurate quantification in food and feedstuff. While most screening methods for mycotoxins are based on immunoassays, unambiguous analyte confirmation can be easily achieved with mass spectrometric methods, like gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). Due to the introduction of atmospheric pressure ionisation (API) techniques in the late 80s, LC/MS has become a routine technique also in food analysis, overcoming the traditional drawbacks of GC/MS regarding volatility and thermal stability. During the last few years, this technical and instrumental progress had also an increasing impact on the expanding field of mycotoxin analysis. The aim of the present review is to give an overview on the application of LC-(API)MS in the analysis of frequently occurring and highly toxic mycotoxins, such as trichothecenes, ochratoxins, zearalenone, fumonisins, aflatoxins, enniatins, moniliformin and several other mycotoxins. This includes also the investigation of some of their metabolites and degradation products. Suitable sample pre-treatment procedures, their applicability for high sample through-put and their influence on matrix effects will be discussed. The review covers literature published until July 2006.     

食品中霉菌毒素样品前处理及分析方法研究进展

霉菌毒素广泛存在于食物和动物饲料中,可经食物链传递危及动物与人体健康,带来严重的食品安全问题。食品基体复杂,霉菌毒素结构多样、含量极低,其分离分析需要高效的前处理技术及快速灵敏的分析方法。该文综述了基于分子印迹聚合物、量子点材料、石墨烯类碳材料、生物材料等新型分离介质的固相(微)萃取、液相(微)萃取、免疫亲和层析、磁分离等样品前处理技术及液相色谱-质谱、免疫分析法、生物传感器等分析方法在食品霉菌毒素分析中的应用,并展望了其发展趋势。     

LC-MS/MS-based multibiomarker approaches for the assessment of human exposure to mycotoxins

Mycotoxins are toxic fungal secondary metabolites that frequently contaminate food and feed worldwide, and hence represent a major hazard for food and feed safety. To estimate human exposure arising from contaminated food, so-called biomarker approaches have been developed as a complementary biomonitoring tool besides traditional food analysis. The first methods based on radioimmunoassays and enzyme-linked immunosorbent assays as well as on liquid chromatography were developed in the late 1980s and early 1990s for the carcinogenic aflatoxins and in the last two decades further tailor-made methods for some major mycotoxins have been published. Since 2010, there has been a clear trend towards the development and application of multianalyte methods based on liquid chromatography–electrospray ionization tandem mass spectrometry for assessment of mycotoxin exposure made possible by the increased sensitivity and selectivity of modern mass spectrometry instrumentation and sophisticated sample cleanup approaches. With use of these advanced methods, traces of mycotoxins and relevant breakdown and conjugation products can be quantified simultaneously in human urine as so-called biomarkers and can be used to precisely describe the real exposure, toxicokinetics, and bioavailability of the toxins present. In this article, a short overview and comparison of published multibiomarker methods focusing on the determination of mycotoxins and relevant excretion products in human urine is presented. Special attention is paid to the main challenges when analyzing these toxic food contaminants in urine, i.e., very low analyte concentrations, appropriate sample preparation, matrix effects, and a lack of authentic, NMR-confirmed calibrants and reference materials. Finally, the progress in human exposure assessment studies facilitated by these analytical methods is described and an outlook on probable developments and possibilities is presented.

Mimotopes for Mycotoxins Diagnosis Based on Random Peptides or Recombinant Antibodies from Phage Library

Mycotoxins, the small size secondary metabolites of fungi, have posed a threat to the safety of medicine, food and public health. Therefore, it is essential to create sensitive and effective determination of mycotoxins. Based on the special affinity between antibody and antigen, immunoassay has been proved to be a powerful technology for the detection of small analytes. However, the tedious preparation and instability of conventional antibodies restrict its application on easy and fast mycotoxins detection. By virtue of simplicity, ease of use, and lower cost, phage display library provides novel choices for antibodies or hapten conjugates, and lead random peptide or recombinant antibody to becoming the promising and environmental friendly immune-reagents in the next generation of immunoassays. This review briefly describes the latest developments on mycotoxins detection using M13 phage display, mainly focusing on the recent applications of phage display technology employed in mycotoxins detection, including the introduction of phage and phage display, the types of phage displayed peptide/recombinant antibody library, random peptides/recombinant antibodies-based immunoassays, as well as simultaneous determination of multiple mycotoxins.     

Application of Biomarkers to Assessment of Risk to Human Health from Exposure to Mycotoxins

Mycotoxins, the toxic compounds produced by mold secondary metabolism, represent a relevant source of danger to humans through alimentary channels. Efforts have been made by researchers and by national authorities to assess mycotoxin incidence in food, but often results are to be considered approximate or inaccurate due to the huge difficulties posed by sampling procedures. More recently the evaluation of mycotoxins in biological fluids have been given increasing attention since the results may offer valuable indications, although general on the overall status of mycotoxin contamination in food and feed. The assessment of the degree of exposure to these contaminants in the population or in specific groups can also be pursued. Researches on mycotoxins in biological fluids greatly contribute to clarify the mechanism of health impairment attributable to these toxic compounds and to elucidate the dose–response relationship. Despite the considerable efforts devoted to mycotoxin research in the past few decades, improvements in methodology has to be achieved mainly in sampling procedures and in quality assurance of the laboratories involved in mycotoxin analysis, as well as in the selection of appropriate biomarkers.     

Evaluation of mycotoxins and their metabolites in human breast milk using liquid chromatography coupled to high resolution mass spectrometry

Humans can be exposed to mycotoxins through the food chain. Mycotoxins are mainly found as contaminants in food and could be subsequently excreted via biological fluids such as urine or human breast milk in native or metabolised form. Since breast milk is usually supposed as the only food for new-borns, the occurrence of mycotoxins in thirty-five human milk samples was evaluated by a newly developed method based on QuEChERS extraction and UHPLC–HRMS detection. The method described here allows the detection of target mycotoxins in order to determine the quality of this initial feeding. The method has been fully validated, with recoveries ranging from 64% to 93% and relative standard deviations (RSD, %) being lower than 20%. Using the method described, non-metabolised mycotoxins such as ZEA, NEO, NIV, ENA, ENA₁, ENB, ENB₁ and metabolites, such as ZEA metabolites, HT-2, DOM and T-2 triol were detected in human milk samples. Results obtained help to estimate the exposure of mothers and infants to mycotoxins. Moreover, to the best of our knowledge, this is the first work describing the simultaneous detection, quantification and screening of mycotoxins and their metabolites in human mature milk.     

食品中真菌毒素样品前处理方法的研究进展

真菌毒素是由真菌在一定环境条件下产生的一类具有毒性的小分子次级代谢产物。真菌毒素种类多,毒性强,污染范围广,可经食物链直接或间接进入人体,危及人体健康。食品基质形态多样,成分复杂,而实际样品中真菌毒素含量低,难以直接对目标物进行分析,故高效的样品前处理技术能实现待测物的分离和富集,在实际样品的分析中尤为重要。该文主要综述了基于磁性纳米材料、石墨烯类材料、分子印迹材料、免疫亲和材料、适配体功能材料等新型分离介质的液相萃取技术、固相萃取技术、场辅助提取技术（磁性固相萃取、超声辅助提取、微波辅助提取）、免疫亲和柱法、QuEChERS法等前处理技术在食品中真菌毒素分析中的应用,并对其分析的发展趋势进行了展望。     

Natural toxins: risks,regulations and the analytical situation in Europe

Natural toxins in food and feed are considered important food safety issues of growing concern, in particular mycotoxins, phycotoxins and plant toxins. Most scientific developments have occurred in the past few decades in the area of mycotoxins. Formal health risk assessments have been carried out by the Joint Expert Committee on Food Additives of the World Health Organization and the Food and Agriculture Organization. Limits and regulations for mycotoxins in food and feed have been established in many countries, including practically all European countries. An array of (formally validated) analytical methods and (certified) reference materials have become available. Several European research projects, funded by the European Commission and supported by the European Standardization Committee, have significantly contributed to this development. Quantitative methods of analysis for mycotoxins often make use of immunoaffinity cleanup with liquid chromatographic or gas chromatographic separation techniques in combination with various types of detectors, including mass spectroscopy. For screening purposes (bio)sensor-based techniques are among the promising newcomers. For the phycotoxins the situation is less advanced. Formal risk assessments by authoritative international bodies have not been carried out. Methods of analysis, formally validated according to internationally harmonized protocols, are scarce and animal testing still plays a key role in official methodology. The development of the analytical methodology is partly hampered by the limited availability of certain reliable calibrants and reference materials, although this situation is gradually improving. New regulations in the European Union have increased the pressure to develop and validate chemical methods of analysis. Joint efforts in the European context are now directed towards significantly improving this situation, and techniques such as liquid chromatography–mass spectroscopy offer promise in this respect. Both the working group on biotoxins of the European Standardization Committee and the network of National Reference Laboratories for Marine Biotoxins have taken up responsibilities here. The plant toxins are a category of natural toxins, where the situation is the least developed with respect to regulations, validated methods of analysis and reference materials. Yet, their occurrence in a wide range of consumable plant species demands the attention of the analytical community.     

固相萃取材料在食品真菌毒素检测中的研究进展

被真菌毒素污染的食品可引发严重的健康问题,如癌症和畸形等,已成为全球公共卫生关注的焦点。因此,精准检测食品中痕量真菌毒素对保障人类健康具有重要意义。真菌毒素在食品中的浓度水平较低且易与复杂的食品基质成分结合,基质干扰严重影响检测的灵敏度,需采用有效的样品前处理技术进行富集和净化。固相萃取作为一种高效的样品前处理技术,其关键取决于萃取材料。该文总结了过去5年固相萃取材料在食品中真菌毒素样品前处理方面的研究进展,并对未来发展方向进行了展望,以期为食品中真菌毒素快速高效分析方法的开发提供参考。     

Nanoparticle-based immunosensors and immunoassays for aflatoxins

Aflatoxins are naturally existing mycotoxins produced mainly by Aspergillus flavus and Aspergillus parasiticus, present in a wide range of food and feed products. Because of their extremely high toxicity and carcinogenicity, strict control of maximum residue levels of aflatoxins in foodstuff is set by many countries. In daily routine, different chromatographic methods are used almost exclusively. As supplement, in several companies enzyme immunoassay-based sample testing as primary screening is performed. Recently, nanomaterials such as noble metal nanoparticles, magnetic particles, carbon nanomaterials, quantum dots, and silica nanomaterials are increasingly utilized for aflatoxin determination to improve the sensitivity and simplify the detection. They are employed either as supports for the immobilization of biomolecules or as electroactive or optical labels for signal transduction and amplification. Several nanoparticle-based electrochemical, piezoelectric, optical, and immunodipstick assays for aflatoxins have been developed. In this review, we summarize these recent advances and illustrate novel concepts and promising applications in the field of food safety.     

植物油中真菌毒素检测技术的研究进展

真菌毒素是由丝状真菌或霉菌产生的结构多样的小分子次级代谢产物，常见于粮油中，具有致畸性、肝毒性、肾毒性、致癌性、出血性、免疫抑制及破坏生殖系统等毒性。真菌毒素在基体中存在浓度低、种类多、极性范围广、同族类化合物结构类似、性质接近，定性信息缺乏。植物油是易受真菌毒素污染的食品之一，并且含有大量的油脂、脂肪酸和色素，可能增加基质效应，降低灵敏度，并损坏仪器。因此，建立高效样品前处理方法及高灵敏度、高通量、多种真菌毒素检测技术成为植物油基体中真菌毒素准确测定面临的巨大挑战。该文综述了溶剂提取（LLE）、固相萃取（SPE）、凝胶渗透色谱（GPC）、动态共价化学肼（DCHC）、QuEChERS方法在油中真菌毒素前处理中的应用，分析了气相色谱、液相色谱、液相色谱-串联质谱及免疫传感器等检测技术的特点，并对植物油中真菌毒素污染检测的发展应用进行了展望。     

Mycotoxins: Simultaneous Detection of Zearalenone and Citrinin by Voltammetry on Edge Plane Pyrolytic Graphite Electrode

Mycotoxins are highly toxic compounds often found in the food. It is of paramount importance to have analytical technique for point‐of‐care on‐spot detection for authorised personnel to immediately take the action required. Electrochemistry offers the portability for miniaturized sensor of mycotoxins. Here we show that edge‐plane pyrolytic electrode offers excellent selectivity and sensitivity towards simultaneous detection of zearalenone and citrinin. This will have a great impact for point‐of‐care mycotoxin detection.     

T-2 Toxin—The Most Toxic Trichothecene Mycotoxin: Metabolism,Toxicity, and Decontamination Strategies

Among trichothecenes, T-2 toxin is the most toxic fungal secondary metabolite produced by different Fusarium species. Moreover, T-2 is the most common cause of poisoning that results from the consumption of contaminated cereal-based food and feed reported among humans and animals. The food and feed most contaminated with T-2 toxin is made from wheat, barley, rye, oats, and maize. After exposition or ingestion, T-2 is immediately absorbed from the alimentary tract or through the respiratory mucosal membranes and transported to the liver as a primary organ responsible for toxin''s metabolism. Depending on the age, way of exposure, and dosage, intoxication manifests by vomiting, feed refusal, stomach necrosis, and skin irritation, which is rarely observed in case of mycotoxins intoxication. In order to eliminate T-2 toxin, various decontamination techniques have been found to mitigate the concentration of T-2 toxin in agricultural commodities. However, it is believed that 100% degradation of this toxin could be not possible. In this review, T-2 toxin toxicity, metabolism, and decontamination strategies are presented and discussed.     

Chromatography of Trichothecene Mycotoxins

Abstract

Trichothecene mycotoxins occur in agricultural commodities and can cause problems from feed refusal to death in animals. This paper describes chromatographic methods for selective analysis for trichothecene mycotoxins. These methods include gas chromatography (GC), thin layer chromatography (TLC), and high pressure liquid chromatography (HPLC). The trichothecene analysis methods by GC and TLC are shown to have a greater sensitivity than in HPLC for the underivatized mycotoxins.     

Mycotoxins from Mold Fungi — Weapons of Uninivited Fellow-Boarders of Man and Animal: Structures,Biological Activity,Biosynthesis, and Precautions

In addition to the antibiotics, mycotoxins represent a second large group of biologically active substances of microbial origin. Over 300 mycotoxins are so far known and can be subdivided into 25 structural types. They are formed by approximately 350 molds of which there are 10 000 different strains. As mycotoxin-producing molds tend to spread aggressively on foodstuffs, they can cause epidemic mycotoxicoses.—The mycotoxins have been isolated, their structures determined, and their biological activities investigated; their biosynthesis has now also largely been elucidated. Accordingly, mycotoxins are derived from only three groups of key biogenetic building blocks: polyketides, isopentenyl pyrophosphate, and amino acids. Mycotoxins are mainly non-polar, chemically stable, are formed in high concentrations, and do not contain—unlike antibiotics—any sugars. Mycotoxins display an enormous variety of toxic-pharmacological activities, e.g. liver degradation, hemorrhages, carcinomas. The identification of mycotoxicoses is impeded by their long incubation periods and the fact that the mycotoxins tend to accumulate in the mammalian organism, which means that even very low concentrations in food are a potential danger. The particularly dangerous aflatoxin B₁ 1 may not exceed a limit in food of 5 ppb (5 μg/kg), which is difficult to control.     

液相色谱-飞行时间质谱同时测定粮食中13种真菌毒素

建立了液相色谱-飞行时间质谱(LC-TOF MS)联用技术同时检测小麦和玉米中镰刀菌、曲霉菌和青霉菌产生的13种真菌毒素的分析方法。样品经乙腈-水-乙酸(84∶15∶1,体积比)混合溶剂提取,My-cosep 226多功能净化柱和强阴离子交换柱净化后,采用LC-TOF MS检测。在电喷雾正离子模式下,以保留时间和化合物精确分子离子质量对真菌毒素进行识别,以10 ppm为提取离子窗口进行定量。结果表明,13种真菌毒素在一定的线性范围内线性关系良好,相关系数均大于0.99,质量精确度均小于5 ppm,回收率为70%～113%,相对标准偏差为0.2%～14.5%。该方法可用于粮食中多种真菌毒素的同时测定。