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El pdf del artículo es la versión post-print. ; D-Fagomine is an iminosugar first found in buckwheat (Fagopyrum esculentum Moench) which if used as a dietary supplement or functional food component may reduce the risks of developing insulin resistance, becoming overweight and suffering from an excess of potentially pathogenic bacteria. As D-fagomine may become increasingly important to the food industry, a reliable analytical method for its determination in natural plant sources and foodstuffs is desirable. We have devised a method to separate D-fagomine from its diastereomers 3-epi-fagomine and 3,4-di-epi-fagomine in a single run by cation exchange high-performance liquid chromatography (HPLC) with detection and quantification by mass spectrometry using electrospray ionisation and a simple quadrupole analyser (ESI-Q-MS). The method is validated and applied to the determination of D-fagomine in buckwheat groats (6.7-44 mg kg ?1), leaves, bran and flour.We show that buckwheat contains 3,4-di-epi-fagomine (1.0-43 mg kg ?1), which has not previously been reported in this source. The procedure is also applied to mulberry (Morus alba) leaves, which contain D-fagomine and 3-epi-fagomine as minor components. The new method provides a means for convenient and accurate determination of D-fagomine in plant samples and foodstuffs.© 2011 Springer-Verlag. ; This research was primarily funded by Bioglane SLNE. Financial support from the Spanish Ministry of Science and Innovation (CDTI-NEOTEC 20080474, AGL2009-12374-C03-03/ALI) and the Catalan regional government (Generalitat de Catalunya, 2009 SGR 00281) is also appreciated. ; Peer Reviewed

[Purpose]: Polyphenol metabolites are key mediators of the biological activities of polyphenols. This study aimed to evaluate the long-term effects of a high-fat high-sucrose (HFHS) diet on the metabolism of proanthocyanidins from grape seed extract (GSE). [Methods]: Adult female Wistar–Kyoto rats were fed a standard (STD) or HFHS diet supplemented or not with GSE for 16 weeks. PA metabolites were determined by targeted HPLC–MS/MS analysis. [Results]: A lower concentration of total microbial-derived PA metabolites was present in urine and the aqueous fraction of faeces in the HFHS + GSE group than in the STD + GSE group. In contrast, a tendency towards the formation of conjugated (epi)catechin metabolites in the HFHS + GSE group was observed. [Conclusions]: These results show that a HFHS diet significantly modifies PA metabolism, probably via: (1) a shift in microbial communities not counteracted by the polyphenols themselves; and (2) an up-regulation of hepatic enzymes. ; This research was supported by the Spanish Ministry of Science and Innovation (Grants: AGL2009-12374-C03-01, -02 and -03; and AGL2013-49079-C2-1, 2 and -R, and through a doctoral fellowship to L.M.). The Panamanian Government (SENACYT/IFARHU) awarded a graduate fellowship to E.M.-T. The ISCIII is acknowledged for a "Sara Borrell" postdoctoral contract to J.P.-J. (CD09/00068). ; Peer Reviewed