Plasma and Urine Concentrations of Bioactive Dietary Benzoxazinoids and Their Glucuronidated Conjugates in Rats Fed a Rye Bread-Based Diet

Thorough knowledge of the absorption and metabolism of dietary benzoxazinoids is needed to understand their health promoting effects. In this study, the fates of these bioactive compounds were examined by LC-MS/MS in plasma, urine, and feces after ingesting a daily dose of 4780 +/- 68 nmol benzoxazinoids from rye bread using Wistar rats as a model. HBOA-glc (2-beta-D-glucopyranosyloxy-1,4-benzoxazin-3-one) was the predominant benzoxazinoid in the plasma (74 +/- 27 nmol/L), followed by DIBOA-glc (2-beta-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one) and HBOA. The total level of benzoxazinoids in the urine was 1176 +/- 66 nmol/d, which corresponds to approximately 25% of the total dietary intake. The urinary benzoxazinoid profile differed from that of plasma with HBOA-glc and DIBOA-glc (647 +/- 31 and 466 +/- 33 nmol/d, respectively) as the major urinary components. The glucuronide conjugates of HBOA and DIBOA were detected in both the plasma and urine. N-dehydroxylation was found to be a critical step in the absorption of hydroxamic acids. This unprecedented study will trigger future interest in the biological effects of benzoxazinoids in whole grain rye and wheat diets in humans and other animals.