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.
Monitoring results of food grain contamination with fusariotoxins-deoxynivalenol (DON), zearalenone (ZEN), fumonisins (FB1&FB2), T-2 and HT-2 toxins-are presented. Harvests of 2005-2010 in different regions of Russia were investigated. The occurrence of DON in wheat was 8%, barley 9%, oats 4%, rye 2% and maize 2%. The highest frequency of ZEN contamination was found in oats, the lowest in wheat. Calculated average daily intake of DON varied from 0.066 to 0.096 µg/kg body weight, the highest being found in the Southern region, but substantially lower than the provisional maximum tolerable daily intake. The results of enzyme-linked immunosorbent assay and high-performance liquid chromatography-mass spectrometry analysis demonstrated the presence of T-2 toxin in 14% and HT-2 toxin in 17% of all samples. The maximum level of T-2 toxin was exceeded only in one sample of barley. Relatively high frequency and levels of FB1&FB2 contamination were found in maize.
The authors performed screening of a wide range of mycotoxins by ultra-high-performance liquid chromatography combined with tandem mass spectrometry (UHPLC-MS/MS) in various tea products distributed on the RF market. Samples were selected in retail outlets and obtained from wholesalers. Seventy-seven tea samples were examined: 54 out of them were Camellia sinensis tea, not packed (semi-finished product) and packed; 23 were mono-and multi-component herbal tea. The analytes were 29 mycotoxins including regulated in food products (aflatoxins, ochratoxin A, deoxynivalenol, fumonisins, T-2 toxin and zearalenone), their derivatives and structural analogues (A and B trichothecenes, structural analogues of zearalenone); emergent mycotoxins (sterigmatocystin, mycophenolic acid, moniliformin, enniatins, beauvericin and Alternaria toxins). C. sinensis tea samples, both green and black, were the least contaminated. In contrast, multi-component herbal tea samples tended to be simultaneously contaminated with several mycotoxins (over five) both regulated in food products and emergent ones. Beauvericin, mycophenolic acid and enniatin B were the most frequently detected. Toxigenic properties of mixed tea microflora were examined in vitro. Model experiments were carried out on a substrate consisting of C. sinensis green tea leaves in the absence of any growth factors. Mixed mycoflora from tea, which contained potentially toxigenic species of mold species proved to be capable to simultaneously produce substantial quantities of several mycotoxins including emergent ones. Mycotoxins accumulation amounted to 290 and 5,600 µg/kg of fumonisins B1 and B2 accordingly; 130 µg/kg of zearalenone; 14 µg/kg of sterigmatocystin; 160 µg/kg of alternariol methyl ester. The present survey indicates there is a potential health risk associated with mycotoxins in teas, especially herbal ones. The systematic study of contamination of tea products distributed in the RF with mycotoxins and their producers has been performed for the first time. Long-term monitoring over variety of mycotoxins in this kind of food products is essential for assessing its safety.
Standard solutions of mycotoxins prepared in RP HPLC solvents from neat standards are usually used for analytical method development. Multi-mycotoxin HPLC-MS/MS methods necessitate stability estimation for the wide spectrum of fungal metabolites. The stability of individual diluted stock standard solutions of mycotoxins in RP-HPLC solvents and multi-analyte HPLC-MS/MS calibrants was evaluated under standard storage and analysis conditions. Individual stock standard solutions of aflatoxins, sterigmatocystin, A-and B-trichothecenes, zearalenone and its analogues, ochratoxin A, fumonisins, Alternaria toxins, enniatins and beauvericin, moniliformin, citrinin, mycophenolic, cyclopiazonic acids and citreoviridin were prepared in RP-HPLC solvents and stored at −18 • C for 14 months. UV-spectroscopy was utilized to monitor the stability of analytes, excluding fumonisins. The gradual degradation of α-, β-zearalenol and α-, β-zearalanol in acetonitrile was detected. Aflatoxins and sterigmatocystin, zearalenone, Alternaria toxins, enniatins and beauvericin, citrinin, mycophenolic, cyclopiazonic acids and citreoviridin can be referred to as stable. The concentration of the majority of trichothecenes should be monitored. Diluted multi-mycotoxin standard in water/methanol (50/50 v/v) solutions acidified with 0.1% formic acid proved to be stable in silanized glass at 23 • C exposed to light for at least 75 h (CV ≤ 10%). An unexpected manifestation of MS/MS signal suppression/enhancement was discovered in the course of multi-mycotoxin standard solution stability evaluation. Key Contribution:The stability of the wide spectrum of mycotoxins in individual standard solutions in RP-HPLC solvents and multi-analyte HPLC-MS/MS calibrants under standard storage and analysis conditions is discussed basing on experimental and literature data.
The present issue reviews literature and own research data and gives toxicological and hygienic characteristic of sterigmatocystin. This mycotoxin is produced by fungi of Aspergillus, Bipolaris, Chaetomium, Emiricella species, and is found in cereals, food products (bread, cheese, spices, coffee, dietary supplements) and feed. Sterigmatocystin being a biogenic precursor of aflatoxin B1, has similar chemical structure and exhibits the same toxicological properties, but its toxicity is ten times lower. However, these toxins are rarely detected together. A. versicolor and A. nidulans do not have enzymes necessary for the conversion of sterigmatocystin into aflatoxins, on the contrary, A. flavus and А. parasiticus transform almost all STC into aflatoxins. Sterigmatocystin has been recognized by International Agency for Research on Cancer (IARC) as a 2B carcinogen (possibly carcinogenic to humans). The primary target organ for both mycotoxins is liver. Sterigmatocystin shows mutagenic, toxic and teratogenic effects in animals. Up to date national and international data on sterigmatocystin occurrence in different products is summarized, analytical methods of the determination are reviewed, hygienic assessment of the STC as a priority pollutant is given in the present paper. Also information on STC exposure assessment with regard to different kinds of foodstuff in different countries is being reported, available data on maximum levels of STC in food and feed is discussed. However, data on toxin’s occurrence in food is insufficient for elaboration of hygienic regulations on allowable mycotoxin’s concentration in priority products. Databases Web of Science, PubMed, E-library, CyberLeninka were used when searching the literature.
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