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Doctoral thesis, 2012

Alkylresorcinol metabolites

Marklund, Matti;

Abstract

Alkylresorcinols (AR), a group of phenolic lipids present in the outer parts of wheat and rye, have been evaluated as biomarkers for the intake of whole grain (WG) products of these cereals. AR may be utilized to facilitate the investigation of diet-disease associations in epidemiological studies. In the body, AR are metabolized to two phenolic acids, DHBA and DHPPA, which can be detected in plasma and urine, either as such or as more polar conjugates. The aim of this thesis was to evaluate AR metabolites DHBA and DHPPA as biomarkers for the intake of WG wheat and rye. A gas chromatographic – mass spectrometric method was established that allowed the reliable quantification of AR metabolites in urine samples. This method was comparable to a previously established HPLC-CEAD method. Plasma pharmacokinetics of AR and their metabolites were compared in rats administered intact AR orally or AR metabolites intravenously. The elimination was faster for AR metabolites than for intact AR and the elimination half-lives increased linearly with the number of carbon atoms in the side chain. The formation of metabolites did not differ between rats given shorter or longer AR homologues, indicating that the different homologues were absorbed to a similar extent. Several anthropometric and dietary factors were identified by multivariate statistical tools as potential determinants of urinary AR metabolites and were hypothesized to influence the formation and excretion of AR metabolites at different stages during AR elimination. The reproducibility and relative validity of urinary AR metabolites as biomarkers for the intake of whole grain wheat and rye were assessed in Swedish men and women consuming their habitual diet. AR metabolites were well correlated to self-reported intakes of WG and cereal fibre. The reproducibility of urinary AR metabolites over 2-3 months was dependent on the stability of intake and was higher in 24-h urine collections compared to spot samples. Due to the scarcity of 24-h urine collections in large observational studies and the modest reproducibility in plasma and spot urine samples, the utility of single AR metabolite measurements alone to reflect long-term intakes in epidemiological studies is limited. However, other applications of AR metabolites as biomarkers might prove useful in future studies (e.g., as a compliance check in intervention studies or as reference methods in validations of other dietary assessment tools).

Keywords

alkylresorcinols; metabolites; phenolic acids; rye; wheats; food intake; digestive absorption; analytical methods

Published in

Acta Universitatis Agriculturae Sueciae

2012, number: 2012:24
ISBN: 978-91-576-7660-3
Publisher: Department of Food Science, Swedish University of Agricultural Sciences

Authors' information

Marklund, Matti
Swedish University of Agricultural Sciences, Department of Food Science

UKÄ Subject classification

Nutrition and Dietetics
Food Science

URI (permanent link to this page)

https://res.slu.se/id/publ/38234