New lignan metabolites in rat urine

Ten potential lignan metabolites were quantified in rat urine extracts using liquid chromatography–tandem mass spectrometry. The rats were orally administered with the plant lignans 7-hydroxymatairesinol, matairesinol, lariciresinol or secoisolariciresinol, or with the mammalian lignan enterolactone. The samples were enzymatically hydrolysed and solid-phase extracted before analysis. Of the analysed compounds, only trace amounts of 7-oxoenterolactone could be detected in the urine extracts before administration, but after administration of any of the lignans, the excretion of 7-oxoenterolactone increased and monodemethylated matairesinol and 4,4′-dihydroxyenterolactone could be detected. In addition, other novel lignan metabolites were detected, i.e., 7-oxomatairesinol, α-conidendrin, and α- and β-conidendric acid.