Plasma pharmacokinetics of alkylresorcinol metabolites: new candidate biomarkers for whole-grain rye and wheat intake

Background: Alkylresorcinols are phenolic compounds that are present almost exclusively in rye and wheat fiber. Alkylresorcinols are absorbed and thereafter metabolized to 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), which have been detected in human urine and plasma. Objective: The objective was to determine the plasma pharmacokinetics of DHBA and DHPPA in human subjects to estimate whether they show potential as biomarkers for whole-grain rye and/or wheat intake. Design: Fifteen human volunteers followed a low-alkylresorcinol diet for 2 d before ingesting a single dose of high-fiber rye bread containing 45 mg alkylresorcinols. Plasma samples were collected for 25 h, and the alkylresorcinol metabolites were quantified by HPLC with coulometric electrode array detection. Results: Maximum concentrations were reached at approximate to 6 h for both metabolites, although interindividual variation was found. The half-life was significantly (P < 0.0002) longer for DHPPA(16.3 h) than for DHBA (10.1 h). No significant differences were discovered between women and men in the half-life of each metabolite, which, from a pharmacokinetic point of view, is the most important parameter. The area under the curve differed significantly between DHBA and DHPPA (P < 0.0001) and between women and men (P = 0.03 for DHBA and P = 0.01 for DHPPA). However, when corrected for body weight, the difference between sexes was no longer significant. Conclusions: Our results suggest that DHBA and DHPPA are both good candidate biomarkers for whole-grain rye and/or wheat intake; however, DHPPA is the better indicator because of its longer half-life. This could provide a practical tool when investigating the association between diet and diseases. Am J Clin Nutr 2009; 90: 1167-71.