This study reports on the detailed investigation of human deoxynivalenol (DON) and zearalenone (ZEN) in vivo metabolism through the analysis of urine samples obtained from one volunteer following a naturally contaminated diet containing 138 mu g DON and 10 mu g ZEN over a period of four days. Based on the mycotoxin intake and the concentrations of mycotoxin conjugates in urine, a mass balance was established. The average rates of DON excretion and glucuronidation were determined to be 68 and 76%, respectively. The investigation of formed glucuronides revealed DON-15-glucuronide as main conjugation product besides DON-3-glucuronide. Furthermore, for the first time in human urine a third DON-glucuronide was detected and the fate of ingested masked DON forms (3-acetyl-DON and DON-3-glucoside) was preliminary assessed. The mean excretion rate of ZEN was determined to be 9.4%. ZEN was mainly present in its glucuronide form and in some samples ZEN-14-glucuronide was directly determined 3-10 h after exposure. For the first time concrete figures have become available for the excretion pattern of DON and ZEN-glucuronides throughout a day, the comparison of total DON in 24 h and first morning urine samples and the urinary excretion rate of total ZEN in humans following exposure through naturally contaminated food. Therefore, valuable preliminary information has been obtained through the chosen experimental approach although the study involved only one single individual and needs to be confirmed in larger monitoring studies. The presented experiment contributes to a better understanding of human DON and ZEN in vivo metabolism and thereby supports advanced exposure and risk assessment to increase food safety and examine the relationship between these mycotoxins and potentially associated chronic diseases in the future. (c) 2013 Michael Sulyok. Published by Elsevier Ireland Ltd. All rights reserved.