Structural elucidation of new dimeric ellagitannins from Quercus robur L. roburins A–E

Eight ellagitannins from Quercus robur L. wood have been studied by high-resolution 1H and 13C NMR and FAB-MS spectroscopy. Three of these polyphenols are known compounds, namely, castalagin, vescalagin, and grandinin. Five of the ellagitannins are new oligomeric compounds containing vescalagin or castalagin moieties bonded to a pentose, lyxose or xylose. The inter-unit linkages are carbon–carbon bonds between C-1 of the glucosyl residue of one unit and either the C-2′ of the hexahydroxydiphenoyl (HHDP) group of a second unit or the C-1 of a pentosyl sugar.