Optimization of a Liquid Chromatography−Tandem Mass Spectrometry Method for Quantification of the Plant Lignans Secoisolariciresinol, Matairesinol, Lariciresinol, and Pinoresinol in Foods

A liquid chromatography−tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of the four major enterolignan precursors [secoisolariciresinol, matairesinol, lariciresinol, and pinoresinol] in foods. The method consists of alkaline methanolic extraction, followed by enzymatic hydrolysis using Helix pomatia (H. pomatia) β-glucuronidase/sulfatase. H. pomatia was selected from several enzymes based on its ability to hydrolyze isolated lignan glucosides. After ether extraction samples were analyzed and quantified against secoisolariciresinol-d8 and matairesinol-d6. The method was optimized using model products: broccoli, bread, flaxseed, and tea. The yield of methanolic extraction increased up to 81%, when it was combined with alkaline hydrolysis. Detection limits were 4−10 μg/(100 g dry weight) for solid foods and 0.2−0.4 μg/(100 mL) for beverages. Within- and between-run coefficients of variation were 6−21 and 6−33%, respectively. Recovery of lignans added to model products was satisfactory (73−123%), except for matairesinol added to bread (51−55%). Keywords: Lignans; HPLC-MS/MS; phytoestrogens; secoisolariciresinol; matairesinol; lariciresinol; pinoresinol