Occurrence and partial characterization of polymeric ellagitannins in Quercus petraea Liebl. and Q. robur L. wood

Abstract

To study the polymerised forms of ellagitannins from Quercus robur and Q. petraea heartwood, we analysed the changes in ellagitannins during wood ageing, then the partially characterized soluble polymeric ellagitannins (EPs) and finally the conditions required for the formation of polymeric forms of ellagitannins (H 2 O 2 , Cu 2+ ). Polymeric soluble ellagitannins were extracted from an acetone/water extract of wood samples. Size exclusion chromatography allowed a good separation of number-average molecular weight polymers, oligomers and phenols. Total phenols were estimated by the Folin–Ciocalteu method; the purity and polymeric aspect of EPs were investigated by NMR experiments and thioacidolysis. We noted that the duraminization process and oxidation were the main reactions occurring during polymeric changes in heartwood; the reactions were principally Fenton's radical oxidation. .