, 2012). This could also be due to the low dose ingested and the low sensitivity of the method with estimated LOD values of 0.5 μg/L and 3.0 μg/L for DON-3-Glc and 3ADON, respectively.
However, given the 3ADON intake of 20 μg/d, a mean urine volume of 2.42 L/d and assuming the excretion rate of DON (72%), approximately 6 μg/L should be recovered in urine, a concentration that should indeed be detectable. The same applies for DON-3-Glc (calculated concentration ca. 2 μg/L using the same assumptions). Another reason could be a low bioavailability and subsequent excretion of conjugated forms via feces as recently indicated for rat ( Nagl et al., 2012). small molecule library screening A quantity of 10 μg zearalenone was ingested each day of intervention. The great majority (94%) originated from the maize porridge which
was consumed for lunch (12:30–1:00 pm). Due to the more complex metabolism of zearalenone resulting in various degradation and conjugation products and limited sensitivity of the applied method toward its main urinary excretion product ZEN-14-GlcA, it was not possible to evaluate ZEN metabolism directly as in the case of DON. Therefore, 24 h urine samples were enzymatically hydrolysed to measure free ZEN and ZEN-GlcA combined as total ZEN AZD9291 cell line to reach detectable concentrations. During the intervention diet, the 24 h urine samples contained on average 0.39 μg/L total ZEN (range 0.30–0.59 μg/L) Roflumilast as reported in Fig. 3. This corresponds to a daily excretion of 0.94 μg and a rate of 9.4% (range 7.0–13.2%), when taking the urine volume (mean 2.42 L) into account. This is in the same range as in the experiment of Mirocha and coworkers (1981) where the total ZEN intake was 10.000 times higher (100 mg), whereof approximately 10–20% were recovered in the 24 h
urine (Metzler et al., 2010). However, in this single experiment ZEN was not ingested via naturally contaminated food and in an unrealistic high concentration. ZEN-14-GlcA was directly determined in some spot urine samples 3–10 h after lunch on days 3, 5 and 6 (see Fig. 2). This indicates rapid formation and excretion of ZEN-14-GlcA. Interestingly, it was never found in first morning samples. The quantity of ZEN ingested in this study corresponds to a dose slightly below the TDI of the SCF (83%, confirm Table 2). Hence, it can be concluded that it is likely to determine ZEN-14-GlcA in case of TDI exceedance using our method. For confirmation and more precise estimates of ZEN exposure, it is recommended to hydrolyse suspected samples to re-measure for total free ZEN. Because the employed multi-biomarker method is also capable to detect biomarkers of other mycotoxins, all samples were screened for those was well. However, as expected based on the experience that the method is suitable to detect moderate to high exposures but not the very low background concentrations of nivalenol (4 μg/d), T2/HT2 (2.