Thermal Reaction Products of Ochratoxin A: Metabolism and Bioavailability

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Various chemical reactions are responsible for the degradation of the mycotoxin Ochratoxin A (OTA) during thermal food processing, e.g. during roasting of coffee or extrusion cooking of grain. In the first funding period we could show for the first time that besides the isomerization of OTA to 14R-ochratoxin A (14R-OTA) a covalent matrix-binding of OTA to polysaccharides occurs. Furthermore we could show that these matrix-bound forms are cleaved either during the brewing of coffee or during the intestinal metabolism leading to the release of OTA. In addition to the first funding period we analyzed blood samples of coffee and non-coffee drinkers for the occurrence of OTA and 14R-OTA. We could show that 14R-OTA is detectable in relatively high levels in blood samples in some cases with even higher levels compared to OTA. In the following proposal the reasons for these high levels will be studied. For this in vitro studies for mechanistic evaluations as well as in vivo studies with humans are planned. During the in vitro experiments the binding to plasma proteins, the metabolism in liver and kidney microsomes as well as the intestinal metabolism using the pig-cecum-model will be studied in comparison of OTA and 14R-OTA. In vivo the plasma concentration of 14R-OTA will be screened depending on the consumption of 14R-OTA-containing food samples, especially coffee. In order to detect further sources for 14R-OTA exposure, relevant food groups will be analyzed with the main focus on thermal processed samples.With the obtained data concerning occurrence, metabolism and bioavailability of 14R-OTA the toxicological relevance for the consumer will be evaluated.