Abstract
The mycotoxin ochratoxin A is a secondary metabolite occurring in a wide range of commodities. During the exposure of ochratoxin A to white and blue light, a cleavage between the carbon atom C-14 and the nitrogen atom was described. As a reaction product, the new compound ochratoxin α amide has been proposed based on mass spectrometry (MS) experiments. In the following study, we observed that this compound is also formed at high temperatures such as used for example during coffee roasting and therefore represents a further thermal ochratoxin A degradation product. To confirm the structure of ochratoxin α amide, the compound was prepared in large scale and complete structure elucidation via nuclear magnetic resonance (NMR) and MS was performed. Additionally, first studies on the toxicity of ochratoxin α amide were performed using immortalized human kidney epithelial (IHKE) cells, a cell line known to be sensitive against ochratoxin A with an IC50 value of 0.5 μM. Using this system, ochratoxin α amide revealed no cytotoxicity up to concentrations of 50 μM. Thus, these results propose that the thermal degradation of ochratoxin A to ochratoxin α amide might be a detoxification process. Finally, we present a sample preparation and a HPLC-tandem mass spectrometry (HPLC-MS/MS) method for the analysis of ochratoxin α amide in extrudates and checked its formation during the extrusion of artificially contaminated wheat grits at 150 and 180 °C, whereas no ochratoxin α amide was detectable under these conditions.
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Acknowledgments
The authors thank ABSciex for supplying us with a QTRAP 5500 mass spectrometer, Merck VWR for supplying us with a VWR Hitachi LaChrom Ultra HPLC system, Rolf Geisen for providing P. nordicum BFE487, K. Bergander for NMR measurements, and A. Klusmeier-König for the performed cell culture experiments.
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The authors thank the Deutsche Forschungsgemeinschaft (HU 730/10-1) for the financial support.
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Bittner, A., Cramer, B., Harrer, H. et al. Structure elucidation and in vitro cytotoxicity of ochratoxin α amide, a new degradation product of ochratoxin A. Mycotoxin Res 31, 83–90 (2015). https://doi.org/10.1007/s12550-014-0218-y
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DOI: https://doi.org/10.1007/s12550-014-0218-y