Human plasma kinetics and relative bioavailability of alkylresorcinols after intake of rye bran

Alkylresorcinols (ARs) are phenolic lipids present in whole grain and bran of wheat and rye. Chemically, they comprise 1,3-dihydroxy-5-alkylbenzene homologs with odd-numbered, mainly saturated hydrocarbon side chains in the range of 17-25 carbon atoms. ARs are evaluated both for physiological effects and for their potential use as biomarkers of whole-grain wheat and rye intake. In this study, plasma kinetics and relative bioavailability of ARs in humans were investigated after a single intake of rye bran 120 g (190 mg ARs). The shapes of plasma concentration time curves were similar in the subjects (n = 6) with 2 peaks at similar to 2.8 and 6.5 h and maximum concentrations (mean +/- SEM) of 1253 +/- 125 and 3365 +/- 309 nmol/L, respectively. The relative bioavailability of different homologs increased with increasing length of the AR side chain (r = 0.97, P < 0.001), indicating differences in metabolism. The apparent half-lives were rather short, similar to 5 h for all homologs, which suggests that the AR concentration in plasma could be used as a short- to medium-term biomarker of regular intake of whole-grain wheat and rye.