Original

Wood Science and Technology

, Volume 47, Issue 3, pp 523-535

MALDI-TOF, HPLC-ESI-TOF and 13C-NMR characterization of chestnut (Castanea sativa) shell tannins for wood adhesives

  • Gonzalo VázquezAffiliated withDepartment of Chemical Engineering, School of Engineering, University of Santiago de Compostela
  • , Antonio PizziAffiliated withENSTIB-LERMAB, Nancy Université
  • , M. Sonia FreireAffiliated withDepartment of Chemical Engineering, School of Engineering, University of Santiago de Compostela
  • , Jorge SantosAffiliated withDepartment of Chemical Engineering, School of Engineering, University of Santiago de Compostela
  • , Gervasio AntorrenaAffiliated withDepartment of Chemical Engineering, School of Engineering, University of Santiago de Compostela
  • , Julia González-ÁlvarezAffiliated withDepartment of Chemical Engineering, School of Engineering, University of Santiago de Compostela Email author 

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Abstract

MALDI-TOF, HPLC-ESI-TOF and 13C-NMR techniques were used to analyse the structure of non-purified aqueous chestnut shell tannin extracts. In addition, the influence of the extraction agent (water or aqueous solutions of Na2SO3 and/or NaOH) on tannin structure was analysed by MALDI-TOF in order to select the extract with the best properties for wood adhesives. Using HPLC-ESI-TOF, catechin/epicatechin, gallocatechin/epigallocatechin, dicatechin structures, dicatechin structures without a hydroxyl group, galloyl-glucoses and ellagic acid were identified as the main monomeric components in the aqueous extract. 13C-NMR and MALDI-TOF spectra revealed that extracts are mostly composed of procyanidin and prodelphinidin structures although prorobinetidins might be also present. MALDI-TOF spectrometry was used to identify the extract oligomeric components. Extractions with Na2SO3 and/or NaOH produced changes in the predominant structures in the extracts and on the amount of sugar units linked to the flavonoid structures, which decreased in the presence of Na2SO3. Extract obtained using low Na2SO3 and NaOH concentrations (1.5 and 0.75 %, respectively) was selected as more suitable for wood adhesive preparation.