Urinary biomarkers of exposure to the mycoestrogen zearalenone and its modified forms in German adults

Zearalenone (ZEN), a mycotoxin with estrogenic activity, can exert adverse endocrine effects in mammals and is thus of concern for humans. ZEN is found in cereal crops and grain-based foods, often along with modified ('masked') forms usually not detected in routine contaminant analysis, e.g., ZEN-O-beta-glucosides and ZEN-14-sulfate. These contribute to mycoestrogen exposure, as they are cleaved in the gastrointestinal tract to ZEN, and further metabolized in animals and humans to alpha- and beta-zearalenol (alpha-ZEL and beta-ZEL). ZEN and its metabolites are mainly excreted as conjugates in urine, allowing to monitor human exposure by a biomarker-based approach. Here, we report on a new study in German adults (n = 60) where ZEN, alpha-ZEL, and beta-ZEL were determined by LC-MS/MS analysis after enzymatic hydrolysis and immunoaffinity column clean-up of the aglycones in urines. Biomarkers were detected in all samples: ZEN ranges 0.04-0.28 (mean 0.10 +/- 0.05; median 0.07) ng/mL; alpha-ZEL ranges 0.06-0.45 (mean 0.16 +/- 0.07; median 0.13) ng/mL, and beta-ZEL ranges 0.01-0.20 (mean 0.05 +/- 0.04; median 0.03) ng/mL. Notably, average urinary levels of alpha-ZEL, the more potent estrogenic metabolite, are higher than those of ZEN, while beta-ZEL (less estrogenic than ZEN) is found at lower levels than the parent mycotoxin. Similar results were found in ten persons who collected multiple urine samples to gain more insight into temporal fluctuations in ZEN biomarker levels; here some urines had higher maximal concentrations of total ZEN (the sum of ZEN, alpha-ZEL, and beta-ZEL) with 1.6 and 1.01 ng/mL, i.e., more than those found in the majority of other urines. A preliminary approach to translate the new urinary biomarker data into dietary mycotoxin intake suggests that exposure of most individuals in our cohort is probably below the tolerable daily intake (TDI) of 0.25 mu g/kg b.w. set by EFSA as group value for ZEN and its modified forms while that of some individuals exceed it. In conclusion, biomonitoring can help to assess consumer exposure to the estrogenic mycotoxin ZEN and its modified forms and to identify persons at higher risk.