Guidance for the assessment of detoxification processes in feed.

This statement provides scientific guidance on the information needed to support the risk assessment of the detoxification processes applied to products intended for animal feed in line with the acceptability criteria of the Commission Regulation (EU) 2015/786.

Decontamination process for dioxins and dioxin-like PCBs from fish oil and vegetable oils and fats by a physical process with activated carbon.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) assessed a decontamination process of fish oils and vegetable oils and fats to reduce the concentrations of dioxins (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, abbreviated together as PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) by adsorption to activated carbon. All feed decontamination processes must comply with the acceptability criteria specified in the Commission Regulation (EU) 2015/786. Data provided by the feed food business operator (FBO) were assessed for the efficacy of the process and to demonstrate that the process did not adversely affect the characteristics and properties of the product. The limited information provided, in particular on the analysis of the samples before and after decontamination, did not allow the CONTAM Panel to conclude whether or not the proposed decontamination process is effective in reducing PCDD/Fs and DL-PCBs in the fish- and vegetable oils and fats. Although there is no evidence from the data provided that the decontamination process leads to detrimental changes in the nutritional composition of the fish- and vegetable oils, it is possible that the process could deplete some beneficial constituents (e.g. vitamins). Taken together, it was not possible for the CONTAM Panel to conclude that the decontamination process as proposed by the FBO is compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Evaluation of the risks for animal health related to the presence of hydroxymethylfurfural (HMF) in feed for honey bees.

The European Commission has asked the EFSA to evaluate the risk for animal health related to the presence of hydroxymethylfurfural (HMF) in honey bee feed. HMF is a degradation product of particular sugars and can be present in bee feed. HMF is of low acute toxicity in bees but causes increased mortality upon chronic exposure. A benchmark dose lower limit 10% (BMDL10) of 1.16 µg HMF per bee per day has been calculated from mortalities observed in a 20-day study and established as a Reference Point covering also mortality in larvae, drones and queens for which no or insufficient toxicity data were available. Winter bees have a much longer lifespan than summer bees and HMF shows clear time reinforced toxicity (TRT) characteristics. Therefore, additional Reference Point intervals of 0.21-3.1, 0.091-1.1 and 0.019-0.35 µg HMF/bee per day were calculated based on extrapolation to exposure durations of 50, 90 and 180 days, respectively. A total of 219 analytical data of HMF concentrations in bee feed from EU Member States and 88 from Industry were available. Exposure estimates of worker bees and larvae ranged between 0.1 and 0.48, and between 0.1 and 0.51 µg HMF/per day, respectively. They were well below the BMDL10 of 1.16 µg HMF/bee per day, and thus, no concern was identified. However, when accounting for TRT, the probability that exposures were below established reference point intervals was assessed to be extremely unlikely to almost certain depending on exposure duration. A concern for bee health was identified when bees are exposed to HMF contaminated bee feed for several months.

Assessment of an application on a detoxification process of groundnut press cake for aflatoxins by ammoniation.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) provided a scientific opinion on an application for a detoxification process of groundnut press cake for aflatoxins by ammoniation. Specifically, it is required that the feed decontamination process is compliant with the acceptability criteria specified in the Commission Regulation (EU) 2015/786 of 19 May 2015. The CONTAM Panel assessed the data provided by the feed business operator with respect to the efficacy of the process to remove the contaminant from groundnut press cake batches and on information demonstrating that the process does not adversely affect the characteristics and the nature of the product. Although according to the literature the process may be able to reduce aflatoxin levels below the legal limits, the Panel concluded that the proposed decontamination process, on the basis of the experimental data submitted by the feed business operator, cannot be confirmed for compliance with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015. The Panel recommended sufficient sample testing before and after the process, under the selected conditions, to ensure that the process is reproducible and reliable and to demonstrate that the detoxification is not reversible. In addition, genotoxicity testing of extracts of the treated feedingstuff and of the identified degradation products would be necessary. Finally, information on the transfer rate of AFB1 to AFM1 excretion in milk for animals fed the ammoniated product, in comparison to the starting material and on the ammoniation process changes of the nutritional values of the feed material should be provided.

DNA reactivity of altertoxin II: Identification of two covalent guanine adducts formed under cell-free conditions.

Fungi of the genus Alternaria infest many agricultural crops and produce numerous mycotoxins, of which altertoxin II (ATX II) is one of the most mutagenic metabolites. ATX II carries an epoxide group but the formation of DNA adducts has not been demonstrated to date. We report now that ATX II gives rise to two covalent adducts with guanine when incubated with DNA under cell-free conditions. These adducts were demonstrated by LC-high resolution MS after enzymatic degradation of the incubated DNA to deoxynucleosides. The major adduct results from the covalent binding of ATX II, presumably through the epoxide group, to guanine, whereas the minor guanine adduct is derived from the major one by the elimination of two equivalents of water. In addition, a third adduct was detected, formed through covalent binding of ATX II to cytosine followed by the loss of two equivalents of water. The direct DNA reactivity of ATX II may explain its high mutagenicity.

Risk assessment of ochratoxin A in food.

The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 µg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 µg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.

Combined hazard assessment of mycotoxins and their modified forms applying relative potency factors: Zearalenone and T2/HT2 toxin.

This paper describes a methodology for hazard assessment of groups of related substances for which toxicity data are insufficient, and which utilises, next to conventional toxicological assessments and mechanistic information, the derivation of relative toxicity potency factors (RPFs). Zearalenone (ZEN) and T-2 toxin (T2) and HT-2 toxin (HT2) and their modified forms have been used as examples. A tolerable daily intake (TDI) for ZEN of 0.25 µg/kg bw was established. In vitro and in vivo studies suggested that modified forms of ZEN act via the same mode of action as ZEN (oestrogenicity). Results from in vivo uterotrophic assays were used to establish RPFs, allowing inclusion the different modified forms in a group TDI with ZEN. A TDI for the sum of T2/HT2 of 0.02 µg/kg bw per day and an acute reference dose (ARfD) of 0.3 µg/kg bw for the sum of T2/HT2 was established. In vitro studies show that phase I metabolites of T2/HT2 act via a similar mode of action as their parent compounds, namely protein synthesis inhibition with immune- and haematotoxicity. The phase I metabolites as well as conjugates of T2/HT2 and their phase I metabolites can be included in a group TDI with T2/HT2 applying RPFs.

Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels.

In 2016, the EFSA Panel on Contaminants in the Food Chain (CONTAM) published a scientific opinion on the acute health risks related to the presence of cyanogenic glycosides (CNGs) in raw apricot kernels in which an acute reference dose (ARfD) of 20 µg/kg body weight (bw) was established for cyanide (CN). In the present opinion, the CONTAM Panel concluded that this ARfD is applicable for acute effects of CN regardless the dietary source. To account for differences in cyanide bioavailability after ingestion of certain food items, specific factors were used. Estimated mean acute dietary exposures to cyanide from foods containing CNGs did not exceed the ARfD in any age group. At the 95th percentile, the ARfD was exceeded up to about 2.5-fold in some surveys for children and adolescent age groups. The main contributors to exposures were biscuits, juice or nectar and pastries and cakes that could potentially contain CNGs. Taking into account the conservatism in the exposure assessment and in derivation of the ARfD, it is unlikely that this estimated exceedance would result in adverse effects. The limited data from animal and human studies do not allow the derivation of a chronic health-based guidance value (HBGV) for cyanide, and thus, chronic risks could not be assessed.

Assessment of a decontamination process for dioxins and PCBs from fish meal by hexane extraction and replacement of fish oil.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) provided a scientific opinion on the assessment of a decontamination process for fish meal. This process entails solvent (hexane) extraction of fish oil from fish meal to remove dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)) as well as dioxin-like (DL-) and non-dioxin-like (NDL-) polychlorinated biphenyls (PCBs) followed by replacement with decontaminated fish oil. All feed decontamination processes must comply with the acceptability criteria specified in the Commission Regulation (EU) 2015/786. The data provided by the feed business operator were assessed with respect to the efficacy of the process, absence of solvent residues, and on information demonstrating that the process does not adversely affect the nature and characteristics of the product. According to data provided, the process was effective in removing PCDD/Fs and DL-PCBs by approximately 70% and NDL-PCBs by about 60%. The data showed that it is possible to meet the current EU requirements with respect to these contaminants, provided that the level of contamination of untreated fish meal is within the range of the tested batches. It is unlikely that hazardous substances (i.e. hexane) remain in the final product. The Panel considered that there is no evidence that fish oil extraction followed by replacement with decontaminated fish oil leads to detrimental changes in the nutritional composition of the fish meal, although some beneficial constituents (e.g. lipophilic vitamins) might be depleted. The feed business operator submitted information to demonstrate safe disposal of the waste material. The CONTAM Panel concluded that the proposed decontamination process to remove dioxins (PCDD/Fs) and PCBs from fish meal by means of solvent extraction and fish oil replacement was assessed to be compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Assessment of a decontamination process for dioxins and PCBs from fish meal by replacement of fish oil.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) provided a scientific opinion on the assessment of a decontamination process of fish meal. It consisted of extraction of the fish oil, filtration and adsorption with activated carbon, and replacement with decontaminated fish oil in order to reduce the amount of dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)), and dioxin-like (DL-) and non-dioxin-like (NDL-) polychlorinated biphenyls (PCBs). All feed decontamination processes must comply with the acceptability criteria specified in the Commission Regulation (EU) 2015/786. Data provided by the feed business operator were assessed for efficacy of the process and to demonstrate that the process did not adversely affect the characteristics and the nature of the product. The process was effective in removing PCDD/Fs (97%) and DL- and NDL-PCBs (93%). The fish meal produced complied with EU regulations for these contaminants. The Panel considered that the reference to information available in published literature was a pragmatic approach to demonstrate that the replacement of fish oil and the use of activated carbon to adsorb these contaminants does not lead to any detrimental changes in the nature of the fish meal. However, it was noted that the process could deplete some beneficial constituents (e.g. oil-soluble vitamins). Information was provided to demonstrate the safe disposal of the waste material. The CONTAM Panel concluded that on the basis of the information submitted by the feed business operator the proposed decontamination process to remove dioxins (PCDD/Fs) and PCBs from the fish meal by oil extraction followed by replacement with decontaminated fish oil, was compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Appropriateness to set a group health-based guidance value for fumonisins and their modified forms.

The EFSA Panel on Contaminants in the Food Chain (CONTAM) established a tolerable daily intake (TDI) for fumonisin B1 (FB 1) of 1.0 µg/kg body weight (bw) per day based on increased incidence of megalocytic hepatocytes found in a chronic study with mice. The CONTAM Panel considered the limited data available on toxicity and mode of action and structural similarities of FB 2-6 and found it appropriate to include FB 2, FB 3 and FB 4 in a group TDI with FB 1. Modified forms of FBs are phase I and phase II metabolites formed in fungi, infested plants or farm animals. Modified forms also arise from food or feed processing, and include covalent adducts with matrix constituents. Non-covalently bound forms are not considered as modified forms. Modified forms of FBs identified are hydrolysed FB 1-4 (HFB 1-4), partially hydrolysed FB 1-2 (pHFB 1-2), N-(carboxymethyl)-FB 1-3 (NCM-FB 1-3), N-(1-deoxy-d-fructos-1-yl)-FB 1 (NDF-FB 1), O-fatty acyl FB 1, N-fatty acyl FB 1 and N-palmitoyl-HFB 1. HFB 1, pHFB 1, NCM-FB 1 and NDF-FB 1 show a similar toxicological profile but are less potent than FB 1. Although in vitro data shows that N-fatty acyl FBs are more toxic in vitro than FB 1, no in vivo data were available for N-fatty acyl FBs and O-fatty acyl FBs. The CONTAM Panel concluded that it was not appropriate to include modified FBs in the group TDI for FB 1-4. The uncertainty associated with the present assessment is high, but could be reduced provided more data are made available on occurrence, toxicokinetics and toxicity of FB 2-6 and modified forms of FB 1-4.

Appropriateness to set a group health based guidance value for T2 and HT2 toxin and its modified forms.

The EFSA Panel on Contaminants in the Food Chain (CONTAM) established a tolerable daily intake (TDI) for T2 and HT2 of 0.02 µg/kg body weight (bw) per day based on a new in vivo subchronic toxicity study in rats that confirmed that immune- and haematotoxicity are the critical effects of T2 and using a reduction in total leucocyte count as the critical endpoint. An acute reference dose (ARfD) of 0.3 µg for T2 and HT2/kg bw was established based on acute emetic events in mink. Modified forms of T2 and HT2 identified are phase I metabolites mainly formed through hydrolytic cleavage of one or more of the three ester groups of T2. Less prominent hydroxylation reactions occur predominantly at the side chain. Phase II metabolism involves conjugation with glucose, modified glucose, sulfate, feruloyl and acetyl groups. The few data on occurrence of modified forms indicate that grain products are their main source. The CONTAM Panel found it appropriate to establish a group TDI and a group ARfD for T2 and HT2 and its modified forms. Potency factors relative to T2 for the modified forms were used to account for differences in acute and chronic toxic potencies. It was assumed that conjugates (phase II metabolites of T2, HT2 and their phase I metabolites), which are not toxic per se, would be cleaved releasing their aglycones. These metabolites were assigned the relative potency factors (RPFs) of their respective aglycones. The RPFs assigned to the modified forms were all either 1 or less than 1. The uncertainties associated with the present assessment are considered as high. Using the established group, ARfD and TDI would overestimate any risk of modified T2 and HT2.

Assessment of a decontamination process for hydrocyanic acid in linseed intended for use in animal feed.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) provided a scientific opinion on the assessment of a decontamination process for the enzymatic treatment and subsequent heating of linseed, in order to reduce the amount of hydrocyanic acid (HCN) present as cyanogenic glycosides. Specifically, it is required that the feed decontamination process is compliant with the acceptability criteria specified in the Commission Regulation (EU) 2015/786 of 19 May 2015. With this aim, the CONTAM Panel assessed the data provided by the feed business operator with respect to the efficacy of the process to remove the contaminant from the linseed batches and on information demonstrating that the process does not adversely affect the characteristics and the nature of the product. The data enabled the Panel to conclude that in agreement with the literature the process was able to remove HCN by about 90%, and that it is possible to meet the current EU requirements for quality of linseed with respect to HCN, provided the level of contamination of untreated linseed would be within the range of the tested batches. The Panel noted that the amounts of other products formed during the enzymatic process and remaining in the treated material are not of toxicological concern. The experimental data provided by the feed business operator showed that the characteristics of linseed were not adversely affected by the decontamination process. The CONTAM Panel concluded that, on the basis of the information submitted by the feed business operator, the proposed decontamination process to remove HCN from linseed by means of enzymatic release and subsequent evaporation was compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Assessment of decontamination processes for dioxins and dioxin-like PCBs in fish oil by physical filtration with activated carbon.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) provided a scientific opinion on the assessment of decontamination processes involving the adsorption with activated carbon and physical filtration of fish oil in order to reduce the amount of dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)) and dioxin-like polychlorinated biphenyls (DL-PCBs). All feed decontamination processes must comply with the acceptability criteria specified in the Commission Regulation (EU) 2015/786. Two feed business operators provided data on their respective decontamination processes, which were assessed in terms of the efficacy of the process and the absence of adverse effects in the nature and characteristics of the product after decontamination. The processes proved to be able to remove PCDD/Fs (82-95%) and DL-PCBs (26-45%) from the fish oil, depending on the process used by the business operator. Given that the level of contamination is within the range of the tested untreated fish oil, it is possible to meet EU requirements for these contaminants after decontamination. The CONTAM Panel considered both the evidence provided by one of the business operators and information in the available literature to conclude that the proposed processes do not lead to any detrimental changes in the nature of the fish oil. However, the process can deplete some beneficial constituents (e.g. vitamins). Information was provided to demonstrate the safe disposal of the waste material. The CONTAM Panel concluded that, on the basis of the information submitted by the feed business operators, the proposed decontamination processes to remove dioxins (PCDD/Fs) and DL-PCBs from the fish oil by means of activated carbon and physical filtration were compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Appropriateness to set a group health based guidance value for nivalenol and its modified forms.

The EFSA Panel on Contaminants in the Food Chain (CONTAM) reviewed new studies on nivalenol since the previous opinion on nivalenol published in 2013, but as no new relevant data were identified the tolerable daily intake (TDI) for nivalenol (NIV) of 1.2 µg/kg body weight (bw) established on bases of immuno- and haematotoxicity in rats was retained. An acute reference dose (ARfD) of 14 µg/kg bw was established based on acute emetic events in mink. The only phase I metabolite of NIV identified is de-epoxy-nivalenol (DE-NIV) and the only phase II metabolite is nivalenol-3-glucoside (NIV3Glc). DE-NIV is devoid of toxic activity and was thus not further considered. NIV3Glc can occur in cereals amounting up to about 50% of NIV. There are no toxicity data on NIV3Glc, but as it can be assumed that it is hydrolysed to NIV in the intestinal tract it should be included in a group TDI and in a group ARfD with NIV. The uncertainty associated with the present assessment is considered as high and it would rather overestimate than underestimate any risk.

Assessment of a decontamination process for dioxins and dioxin-like PCBs in fish oil by physical filtration with activated carbon.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) provided a scientific opinion on the assessment of a decontamination process consisting in the adsorption with activated carbon and physical filtration of fish oil in order to reduce the amount of dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)) and dioxin-like polychlorinated biphenyls (DL-PCBs). All feed decontamination processes must comply with the acceptability criteria specified in the Commission Regulation (EU) 2015/786. The data provided by the feed business operator were assessed with respect to the efficacy of the process and on information demonstrating that the process does not adversely affect the characteristics and the nature of the product. As described in scientific literature, the process was effective in removing PCDD/Fs (84%) and DL-PCBs (55%), and therefore, it is possible to meet the current EU requirements with respect to these contaminants, assuming that the level of contamination of untreated fish oil was within the range of the tested batches. The Panel considered that the reference to information available in published literature was a pragmatic approach to demonstrate that the use of activated carbon adsorption does not lead to any detrimental changes in the nature of the fish oil; however, it was noted that the process could deplete some beneficial constituents (e.g. vitamins). Information was provided to demonstrate the safe disposal of the waste material. The CONTAM Panel concluded that on the basis of the information submitted by the feed business operator the proposed decontamination process to remove dioxins (PCDD/Fs) and DL-PCBs from the fish oil by means of physical filtration with activated carbon, was compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Sulfoglucosides as Novel Modified Forms of the Mycotoxins Alternariol and Alternariol Monomethyl Ether.

The mycotoxins alternariol and alternariol-9-O-methyl ether have recently been reported to be extensively conjugated with glucose and malonyl glucose in tobacco suspension cells. However, only trace amounts of glucosylated conjugates were detected in tomatoes inoculated with Alternaria alternata in the present study. Instead, mostly sulfate conjugates were observed. In studies using cultures of A. alternata and incubations of alternariol and alternariol-9-O-methyl ether with tomato tissue in the absence of the fungus, it was clarified that sulfate conjugates were produced by the fungus, whereas tomato tissues converted alternariol and alternariol-9-O-methyl ether to glucosylated metabolites. Alternariol-3-sulfate, alternariol-9-sulfate, and alternariol-9-O-methyl ether-3-sulfate were unambiguously identified as fungal metabolites using MS and 1H and 13C NMR spectroscopy. When these sulfate conjugates were incubated with tobacco suspension cells or ex planta tomato tissues, three sulfoglucosides of alternariol and one sulfoglucoside of alternariol-9-O-methyl ether were formed. Using NMR spectroscopy, the chemical structures of alternariol-3-sulfate-9-glucoside, alternariol-9-sulfate-3-glucoside, and alternariol-9-O-methyl ether-3-sulfate-7-glucoside were established. These conjugates were also detected in the A. alternata-inoculated tomato. This is the first report on a mixed sulfate/glucoside diconjugate of a mycotoxin. Diconjugates of this novel type may be formed by all mycotoxins and their phase I metabolites with two or more hydroxyl groups and should be taken into account in the future analysis of modified mycotoxins.

DNA damage and repair kinetics of the Alternaria mycotoxins alternariol, altertoxin II and stemphyltoxin III in cultured cells.

The Alternaria mycotoxins alternariol (AOH) and altertoxin II (ATX II) have previously been shown to elicit mutagenic and genotoxic effects in bacterial and mammalian cells, although with vastly different activities. For example, ATX II was about 50 times more mutagenic than AOH. We now report that stemphyltoxin III (STTX III) is also highly mutagenic. The more pronounced effects of the perylene quinones ATX II and STTX III at lower concentrations compared to the dibenzo-α-pyrone AOH indicate a marked dependence of the genotoxic potential on the chemical structure and furthermore suggest that the underlying modes of action may be different. We have now further investigated the type of DNA damage induced by AOH, ATX II and STTX III, as well as the repair kinetics and their dependence on the status of nucleotide excision repair (NER). DNA double strand breaks induced by AOH due to poisoning of topoisomerase IIα were completely repaired in less than 2h. Under cell-free conditions, inhibition of topoisomerase IIα could also be measured for ATX II and STTX III at low concentrations, but the perylene quinones were catalytic inhibitors rather than topoisomerase poisons and did not induce DSBs. DNA strand breaks induced by ATX II and STTX III were more persistent and not completely repaired within 24h. A dependence of the repair rate on the NER status could only be demonstrated for STTX III, resulting in an accumulation of DNA damage in NER-deficient cells. Together with the finding that the DNA glycosylase formamidopyrimidine-DNA glycosylase (Fpg), but not T4 endonuclease V, is able to generate additional DNA strand breaks measurable by the alkaline unwinding assay, we conclude that the genotoxicity of the perylene quinones with an epoxide group is probably caused by the formation of DNA adducts which may be converted to Fpg sensitive sites.

Conjugation of the mycotoxins alternariol and alternariol monomethyl ether in tobacco suspension cells.

The mycotoxins alternariol (AOH) and alternariol-9-O-methyl ether (AME) carry three and two phenolic hydroxyl groups, respectively, which makes them candidates for the formation of conjugated metabolites in plants. Such conjugates may escape routine methods of analysis and have therefore been termed masked or, more recently, modified mycotoxins. We report now that AOH and AME are extensively conjugated in suspension cultures of tobacco BY-2 cells. Five conjugates of AOH were identified by MS and NMR spectroscopy as ß-D-glucopyranosides (attached in AOH 3- or 9-position) as well as their 6'-malonyl derivatives, and as a gentiobiose conjugate. For AME, conjugation resulted in the d-glucopyranoside (mostly attached in the AME 3-position) and its 6'- and 4'-malonyl derivatives. Pronounced differences were noted for the quantitative pattern of AOH and AME conjugates as well as for their phytotoxicity. Our in vitro study demonstrates for the first time that masked mycotoxins of AOH and AME can be formed in plant cells.