A Review of Current Methods for Analysis of Mycotoxins in Herbal Medicines

Prevalence and Exposure Assessment of Aflatoxins Through Black Tea Consumption in the Multan City of Pakistan and the Impact of Tea Making Process on Aflatoxins

Aflatoxins are the highly toxic secondary metabolites of certain fungi, being mainly produced by Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are classified as group 1 category carcinogens by the International Agency for Research on Cancer (IARC). A large number of food commodities are reported to be contaminated with aflatoxins. Tea is the world's second most consumed beverage and the consumption of tea is increasing day by day. Besides being a source of several health promoting substances, tea leaves are also reported to be contaminated with aflatoxins. However, not a single study is reported from Pakistan regarding the level of aflatoxins in commercially available black tea samples. The current study aimed to quantify the level of aflatoxins in commercially available branded and non-branded black tea samples. The estimated daily intake (EDI) of aflatoxins through branded and non-branded black tea consumption and the health risk assessment based on margin of exposure (MOE) approach was assessed. Furthermore, the impact of local tea making processes on the concentration of aflatoxins in tea beverage (filtrate) was also investigated.

Competitive HRP-Linked Colorimetric Aptasensor for the Detection of Fumonisin B1 in Food based on Dual Biotin-Streptavidin Interaction

Fumonisin B1 (FB1) is the most prevalent and toxic form among fumonisin homologues which are produced by fusarium species and it contaminates various types of food products, posing serious health hazards for humans and animals. In this work, a colorimetric assay for the detection of FB1 has been developed based on competitive horseradish peroxidase (HRP)-linked aptamer and dual biotin-streptavidin interaction. In short, a biotinylated aptamer of FB1 was immobilized on the microplate by biotin-streptavidin binding; the complementary strand (csDNA) of the aptamer was ligated with HRP by biotin-streptavidin binding again to form a csDNA-HRP sensing probe, competing with FB1 to bind to the aptamer. The color change can be observed after the addition of chromogenic and stop solution, thereby realizing the visual detection of FB1. Under optimal conditions, good linearity was observed within the concentration range of 0.5 to 300 ng/mL, with a detection of limit of 0.3 ng/mL. This assay is further validated by spike recovery tests towards beer and corn samples, it provides a simple, sensitive and reliable method for the screening of FB1 in food samples and may be potentially used as an alternative to conventional assays.

Mycotoxin Contamination Concerns of Herbs and Medicinal Plants

Plants and medicinal herbs that are available on the market do not always meet quality and safety standards. One particular concern is the risk of contamination with mycotoxins. Aflatoxins and ochratoxin A are the most frequently described mycotoxins in herbal products and have repeatedly been reported to occur at concentrations which exceed regulatory levels set by the European Union (EU). Possible solutions include enforcing existing limits, and for the new materials, establishing tighter limits and mandate the growth of medicinal plants in EU member countries under more strict conditions.

Current research and prevention of aflatoxins in China

Since their discovery in the 1960s, aflatoxins were found to have a considerable impact on the health of humans and animals as well as the country’s economy and international trade. Aflatoxins are often found in nuts, cereals and animal feeds, which has a significant danger to the food industry. Over the years, several steps have been undertaken worldwide to minimise their contamination in crops and their exposure to humans and animals. China is one of the largest exporters and importers of food and animal feed. As a result, many studies have been carried out in China related to aflatoxins, including their distribution, pollution, detection methods, monitoring, testing and managing. Chinese scientists studied aflatoxins in microbiological, toxicological, ecological effects as well as policies relating to their controlling. China has thus put into practice a number of strategies aiming at the prevention and control of aflatoxins in order to protect consumers and ensure a safe trade of food and feed, and the status and enlargement of these strategies are very important and useful for many consumers and stakeholders in China. Therefore, this article aims at the detriment assessments, regulations, distribution, detection methods, prevention and control of aflatoxins in China. It equally provides useful information about the recent safety management systems in place to fight the contamination of aflatoxins in food and feed in China.

Occurrence and analysis of mycotoxins in domestic Chinese herbal medicines

For time immemorial, Chinese herbal medicines (CHMs) have been widely used in China for disease treatment and promotion of general well-being. However, in recent years, many studies have shown that mycotoxins produced by fungi could contaminate CHMs due to unfavourable pre- or post-harvest conditions, raising major concern for consumer safety. At present, there is a significant focus on developing novel mycotoxin detection methods for analysing CHMs, and numerous studies have aimed to determine which kinds of raw herbal materials are most susceptible to mycotoxin contamination. In this review, we focus on recent advances in understanding and detection of mycotoxins in domestic raw herbal materials and related products from 2000 to 2018. Aspects of mycotoxin contamination of CHMs covered in this review include common mycotoxin contaminants in CHMs, maximum mycotoxin residue limits, analytical methods for mycotoxin detection and their applications and limitations, as well as a brief discussion of the trends in ongoing research.

Detection Methods for Aflatoxin M1 in Dairy Products

Mycotoxins are toxic compounds produced mainly by fungi of the genera Aspergillus, Fusarium and Penicillium. In the food chain, the original mycotoxin may be transformed in other toxic compounds, reaching the consumer. A good example is the occurrence of aflatoxin M1 (AFM1) in dairy products, which is due to the presence of aflatoxin B1 (AFB1) in the animal feed. Thus, milk-based foods, such as cheese and yogurts, may be contaminated with this toxin, which, although less toxic than AFB1, also exhibits hepatotoxic and carcinogenic effects and is relatively stable during pasteurization, storage and processing. For this reason, the establishment of allowed maximum limits in dairy products and the development of methodologies for its detection and quantification are of extreme importance. There are several methods for the detection of AFM1 in dairy products. Usually, the analytical procedures go through the following stages: sampling, extraction, clean-up, determination and quantification. For the extraction stage, the use of organic solvents (as acetonitrile and methanol) is still the most common, but recent advances include the use of the Quick, Easy, Cheap, Effective, Rugged, and Safe method (QuEChERS) and proteolytic enzymes, which have been demonstrated to be good alternatives. For the clean-up stage, the high selectivity of immunoaffinity columns is still a good option, but alternative and cheaper techniques are becoming more competitive. Regarding quantification of the toxin, screening strategies include the use of the enzyme-linked immunosorbent assay (ELISA) to select presumptive positive samples from a wider range of samples, and more reliable methods-high performance liquid chromatography with fluorescence detection or mass spectroscopy-for the separation, identification and quantification of the toxin.

Occurrence and Characterization of Fungi and Mycotoxins in Contaminated Medicinal Herbs

Traditional medicinal herbs are widely used and may be contaminated with mycotoxigenic fungi during cultivation, harvesting, and storage, causing spoilage and mycotoxin production. We evaluated the predominant mycoflora and extent of mycotoxin contaminations in 48 contaminated samples of 13 different medicinal herbs. In total, 70.8% of herbs were slightly contaminated with aflatoxins (<5 μg kg-1). Codonopsis radix samples contained ochratoxin A (OTA) (360-515 μg kg-1), and Scutellariae radix samples contained OTA (49-231 μg kg-1) and citrinin (15-53 μg kg-1). Forty samples (83.3%) contained fungal contamination. Sixty-nine strains were characterized via morphological and molecular identification. The predominant mycoflora comprised four genera, Aspergillus spp. (26.1%), Penicillium spp. (24.6%), Rhizopus spp. (14.5%), and Trichoderma spp. (11.6%). Aflatoxins, OTA, and citrinin were detected in 37 cultures by high-performance liquid chromatography-tandem mass spectrometry. Approximately 21.6% of Aspergillus and Penicillium isolates produced mycotoxins. One Penicillium polonicum strain isolated from Scutellariae radix synthesized citrinin. Multiplex PCR analysis showed that three Aspergillus flavus strains harbored aflatoxin biosynthesis genes. One Aspergillus flavus strain isolated from Amomi fructus produced AFB1 and AFB2. To the best of our knowledge, the citrinin production by Aspergillus chevalieri and Penicillium sacculum was first reported in this study, which poses a potential risk of mycotoxin contamination in medicinal herbs.

Aptamer assisted ultrafiltration cleanup with high performance liquid chromatography-fluorescence detector for the determination of OTA in green coffee

One of the most common mycotoxin contaminating feed and foodstuffs is Ochratoxin A (OTA). OTA has a chronic toxic effect and proved to be mutagenic, nephrotoxic, teratogenic, immunosuppressive, and carcinogenic. Aptamer with their specific affinity for OTA was used in this paper to create an analytical technique. Several methods have been reported for the determination of OTA in foods. However, most of these methods could not be applied to a complex food as green coffee because the interfering native fluorescent products made the quantification very difficult. In this work, we mixed two separations based techniques to identify and quantify OTA in green coffee. Aptamer assisted ultrafiltration as separation technique based on the size of molecules was applied to separate the free OTA, the quantification of OTA was established by a high-performance liquid chromatography (HPLC-FD) with a limit of detection (LOD) of 0.05 ng/mL for OTA. Artificially contaminated green coffee displayed a good range of OTA recoveries up to 97.7%. This method can be applied to the quantitative determination of OTA in green coffee at levels below the maximum levels proposed by the European Commission for green coffee. It also confirm that aptamers can be used as biorecognition element in diagnostic assays with commercial application for mycotoxin analysis.

Mycotoxin contamination of food and feed in the Gulf Cooperation Council countries and its detection

Mycotoxins are secondary metabolites produced by different fungal spices and are found in diverse agricultural crops worldwide; they pose a severe threat to public health. Mycotoxins can cause either acute or chronic symptoms, depending on the type and dose of mycotoxin one has been exposed to. Thus, a continuous monitoring of mycotoxins is needed. Since the discovery of mycotoxins, numerous countries, including the Gulf Cooperation Council (GCC) countries, have established mycotoxin-specific regulations for feed and food. Although a number of studies in GCC countries have investigated the presence of mycotoxins, till date, there are no reviews focusing on the mycotoxin contamination of the food and feed from this region. This review is the first study to present an up-to-date overview of the occurrence of mycotoxins in feed and food in the GCC countries and to discuss the techniques used for mycotoxin analysis.

Validated quantitative cannabis profiling for Canadian regulatory compliance - Cannabinoids, aflatoxins, and terpenes

In response to the Canadian federal government's Cannabis Tracking and Licensing System compliance standards, a quantitative method was created for cannabis analysis, and validated using Eurachem V.2 (2014) guidelines. Cannabinol, cannabidiol, cannabigerol, cannabichromene, cannabidiolic acid, cannabigerolic acid, Δ-9-tetrahydrocannabinol, and Δ-9-tetrahydrocannabinolic acid A were all analysed by scheduled multiple reaction monitoring (MRM) via LC-MS/MS and isotope dilution. In addition, aflatoxins B1, B2, G1, and G2 were also analysed by scheduled MRM via LC-MS/MS and matrix matched calibration curves in order to achieve the reporting limits (≤2 μg kg^-1) set out by the European Pharmacopoeia. The LODs/LOQs were 0.50/1.7, 2.0/6.7, 0.59/2.0, and 0.53/1.8 μg kg^-1, for B1, B2, G1, and G2 respectively. Thirty one terpenes were analysed by selected reaction monitoring via GC-MS/MS and isotope dilution using β-myrcene-d₆ as a surrogate. All quantitative analyses can be accomplished using less than 1 g of material, with minimal solvent and consumable use, on low resolution instruments in less than 30 min of instrument time. Of important note is this method's power of selectivity, working ranges, and lack of need for extraction consumables such as SPE or QuEChERS, thereby minimising analytical costs and time.

Recent applications of carbonaceous nanosorbents for the analysis of mycotoxins in food by liquid chromatography: a short review

Carbonaceous nanomaterials (multi-walled carbon nanotubes (MWCNTs), graphene, and graphene oxide (GO)) have attracted attention over the last decade as adsorbents suitable for the analysis of organic and inorganic pollutants. In the present paper we review methods of mycotoxin analysis that involve sample extraction with carbonaceous nanosorbents, reported from 2011 onwards. Recent studies have highlighted the advantages of magnetically modified MWCNTs and GO in mycotoxin analysis, which may enable sample isolation through magnetic separation, reduce the interaction of nanoparticles, and enhance the recovery of analytes. The papers covered in this review point to promising applications of functionalised carbonaceous nanosorbents in mycotoxin analysis. While GO based sorbents can be effective for the adsorption of relatively polar aflatoxins, MWCNTs with high specific surface area and reduced agglomeration achieved through modification with silica and magnetic particles are preferred for the extraction of less polar mycotoxins.

Developments in mycotoxin analysis: an update for 2017-2018

This review summarises developments that have been published in the period from mid-2017 to mid-2018 on the analysis of various matrices for mycotoxins. Analytical methods to determine aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxins, patulin, trichothecenes, and zearalenone are covered in individual sections. Advances in sampling strategies are discussed in a dedicated section, as are methods used to analyse botanicals and spices, and newly developed comprehensive liquid chromatographic-mass spectrometric based multi-mycotoxin methods. This critical review aims to briefly discuss the most important recent developments and trends in mycotoxin determination as well as to address limitations of the presented methodologies.

Thin Films Sensor Devices for Mycotoxins Detection in Foods: Applications and Challenges

Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of mycotoxins include gas chromatography and high-performance liquid chromatography coupled with mass spectrometry or other detectors (fluorescence or UV detection), thin layer chromatography and enzyme-linked immunosorbent assay. These techniques are generally straightforward and yield reliable results; however, they are time-consuming, require extensive preparation steps, use large-scale instruments, and consume large amounts of hazardous chemical reagents. Rapid detection of mycotoxins is becoming an increasingly important challenge for the food industry in order to effectively enforce regulations and ensure the safety of food and feed. In this sense, several studies have been done with the aim of developing strategies to detect mycotoxins using sensing devices that have high sensitivity and specificity, fast analysis, low cost and portability. The latter include the use of microarray chips, multiplex lateral flow, Surface Plasmon Resonance, Surface Enhanced Raman Scattering and biosensors using nanoparticles. In this perspective, thin film sensors have recently emerged as a good candidate technique to meet such requirements. This review summarizes the application and challenges of thin film sensor devices for detection of mycotoxins in food matrices.

Competitive Immunoassays for the Detection of Small Molecules Using Single Molecule Arrays

Small-molecule detection is important for many applications including clinical diagnostics, drug discovery, and measurements of environmental samples and agricultural products. Current techniques for small-molecule detection suffer from various limitations including low analytical sensitivity and complex sample processing. Furthermore, as a result of their small size, small molecules are difficult to detect using an antibody pair in a traditional sandwich assay format. To overcome these limitations, we developed an ultrasensitive competitive immunoassay for small-molecule detection using Single Molecule Arrays (Simoa). We show that the competitive Simoa assay is approximately 50-fold more sensitive than the conventional ELISA. We performed theoretical calculations to determine the factors that influence the sensitivity of competitive Simoa assays and used them to achieve maximal sensitivity. We also demonstrate detection of small molecules in complex biological samples. We show that the competitive Simoa assay is a simple, fast, and highly sensitive approach for ultrasensitive detection of small molecules.

Mycotoxin Contamination of Beverages Obtained from Tropical Crops

This review is mainly centered on beverages obtained from tropical crops, including tea, nut milk, coffee, cocoa, and those prepared from fruits. After considering the epidemiological data found on the matrices above, the focus was given to recent methodological approaches to assess the most relevant mycotoxins. Aspects such as singularities among the mycotoxin and the beverage in which their were found, and the economic effects and repercussions that the mycotoxin-tainted ingredients have on the beverage industry were pointed out. Finally, the burden of their consumption through beverages, including risk and health effects on humans, was addressed as well.

Mycotoxins in Tea: Occurrence, Methods of Determination and Risk Evaluation

Tea is one of the most popular beverages all over the world. Being an everyday drink for almost everyone, for centuries tea was considered safe and healthy. However, fungal contamination of tea at any stage of commodity production can pose a serious health hazard due to the accumulation of toxic secondary metabolites of moulds. Contemporary research revealed incidences of highly contaminated samples. Mycotoxin transfer from naturally contaminated raw tea into beverage was well studied for ochratoxin A only, and the possible leak of other mycotoxins is discussed. The results of several surveys were combined to evaluate aflatoxin B1 and ochratoxin A contamination levels in black tea and Pu-erh. Exposure estimate to aflatoxin B1 and ochratoxin A due to tea consumption was carried out based on these data. Average contamination level corresponds to the exposure of 3⁻40% (aflatoxin B1) and 5⁻24% (ochratoxin A) of mean overall estimates for different cluster diets. Lack of data does not allow the conclusion for the necessity of public health protection measures. It is necessary to perform representative studies of different kinds of tea for regulated mycotoxins at least. Contemporary techniques for analysis of mycotoxins in tea are summarised in the present review.

Progress on nanostructured electrochemical sensors and their recognition elements for detection of mycotoxins: A review

Nanomaterial-embedded sensors have been developed and applied to monitor various targets. Mycotoxins are fungal secondary metabolites that can exert carcinogenic, mutagenic, teratogenic, immunotoxic, and estrogenic effects on humans and animals. Consequently, the need for the proper regulation on foodstuff and feed materials has been recognized from times long past. This review provides an overview of recent developments in electrochemical sensors and biosensors employed for the detection of mycotoxins. Basic aspects of the toxicity of mycotoxins and the implications of their detection are comprehensively discussed. Furthermore, the development of different molecular recognition elements and nanomaterials required for the detection of mycotoxins (such as portable biosensing systems for point-of-care analysis) is described. The current capabilities, limitations, and future challenges in mycotoxin detection and analysis are also addressed.

Electrochemical Immunosensor for Detection of Aflatoxin B₁ Based on Indirect Competitive ELISA

Mycotoxins are the secondary toxic metabolites produced naturally by fungi. Analysis of mycotoxins is essential to minimize the consumption of contaminated food and feed. In this present work, an ultrasensitive electrochemical immunosensor for the detection of aflatoxin B₁ (AFB₁) was successfully developed based on an indirect competitive enzyme-linked immunosorbent assay (ELISA). Various parameters of ELISA, including antigen⁻antibody concentration, blocking agents, incubation time, temperature and pH of reagents, were first optimized in a 96-well microtiter plate to study the antigen⁻antibody interaction and optimize the optimum parameters of the assay. The optimized assay was transferred onto the multi-walled carbon nanotubes/chitosan/screen-printed carbon electrode (MWCNTs/CS/SPCE) by covalent attachment with the aid of 1-Ethyl-3-(3-dimetylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Competition occurred between aflatoxin B₁-bovine serum albumin (AFB₁⁻BSA) and free AFB₁ (in peanut sample and standard) for the binding site of a fixed amount of anti-AFB₁ antibody. Differential pulse voltammetry (DPV) analysis was used for the detection based on the reduction peak of TMB(ox). The developed immunosensor showed a linear range of 0.0001 to 10 ng/mL with detection limit of 0.3 pg/mL. AFB₁ analysis in spiked peanut samples resulted in recoveries between 80% and 127%. The precision of the developed immunosensor was evaluated by RSD values (n = 5) as 4.78% and 2.71% for reproducibility and repeatability, respectively.