Digestibility and absorption of deoxynivalenol-3-ß-glucoside in in vitro models

Certain mycotoxins may be present in plant materials as their glucosides. The question is whether these glucosides may be hydrolysed into their parent compounds in the gastro-intestinal tract (GI-tract), thus increasing the exposure. Therefore, the potential hydrolysis of deoxynivalenol-3-ß-glucoside (DON-3G) to deoxynivalenol (DON) was assessed in two in vitro models representing the human upper GI-tract (mouth, stomach and small intestine). In a fed digestion model, there was no evidence of release of DON from DON-3G, spiked at a level of 2,778 µg DON- 3G/kg food. This shows that the conditions in the GI-tract do not result in hydrolysis of this glucoside into the original mycotoxin. The absorption and transformation of DON-3G in the small intestine was assessed in an in vitro model with human Caco-2 cells in a Transwell system. No evidence was found for the transformation of DON-3G to DON by the Caco-2 cells in both the apical or basolateral side in 24 hours (cells were exposed to 2.4 nmol DON- 3G/ml medium). However, when DON itself was added to the apical side an amount of 23% of the spiked DON was detected in the basolateral side after 24 hours (cells were exposed to 2.3 nmol/ml medium). In conclusion, no evidence was found in the in vitro experiments for significant elevated exposure of humans to DON, since DON- 3G was not hydrolysed to DON in the digestion model representing the upper part of the GI-tract and DON-3G was not hydrolysed to DON by the intestinal epithelial Caco-2 cells. It was shown that bioavailability of DON-3G in humans may be low as compared to DON since Caco-2 cells did not absorb DON-3G, in contrast to DON.