The inclusion of (+)-pinoresinol from flaxseed extracts into β-cyclodextrin elucidated by liquid state NMR techniques

(+)-Pinoresinol (PIN) is a relevant lignan found in flaxseed-derived extracts, but its direct NMR identification in complex food matrices is difficult because of signal overlap and low concentration. In this work, we propose an NMR-based strategy for the selective identification of PIN directly in a multicomponent flaxseed extract. The method combines ¹H NMR spectral pattern recognition, quantitative ³¹P NMR analysis of phenolic hydroxyl groups, and selective spiking experiments. Structural validation was obtained by characterizing the pure PIN/β-cyclodextrin (β-CD) inclusion complex through chemical shift variation analysis, ROESY, and DOSY, which supported a predominant 1:1 stoichiometry in solution. The binding constant was calculated from UV-Vis spectra applying the Benesi-Hildebrand approach. The agreement between the isolated system and the crude extract indicates supramolecular recognition of PIN within the natural matrix. Overall, this study provides an NMR-based approach for the identification of minor lignans in food-derived extracts and supports its application to complex food systems.