Composition of suberin extracted upon gradual alkaline methanolysis of Quercus suber L. cork

The monomeric composition of suberin extracts obtained by gradual alkaline methanolysis of Quercus suber cork was determined by gas chromatography-mas s spectrometry (GC-MS). Results show that l-alkanols and alkanoic and a,ome ga-alkanedioic acids are preferentially removed upon mild alkaline conditio ns, whereas mid-chain-modified omega-hydroxyalkanoic acids are preferential ly removed under stronger alkaline conditions. Saturated w-hydroxyalkanoic acids are found to be abundant in all suberin extracts. These results are c onsistent with two distinct suberin fractions with different locations in c ork cell walls and/or esterification degrees. It is proposed that these fra ctions correlate with the two main suberin peaks in the solid state C-13 NM R spectra of cork and suberin extracts. Quantitative CC-MS analysis showed that suberin monomers comprise similar to 30% (w/w) of the suberin extracts , the remaining comprising nonvolatile structures with high M-n, values, as measured by vapor pressure osmometry. The presence of a large fraction of high molecular weight aliphatic structures in suberin extracts is supported by the corresponding NMR spectra.