A study of variability of suberin composition in cork from Quercus suber L. using thermally assisted transmethylation GC-MS

The chemical composition of suberin in cork from Quercus suber L. was deter mined on virgin and reproduction cork from different sites and trees in Por tugal. Extractive-free samples were analyzed by pyrolysis-gas chromatograph y/mass spectrometry in the presence of tetramethylammonium hydroxide (TMAH) , which provides in situ hydrolysis and (trans)methylation of hydroxyl and carboxyl groups of the suberin monomers. The average chemical monomeric com position of suberin on virgin and reproduction cork is, respectively, alkan oic acids 5.1, 3.3%; alpha,omega -diacids 11.2, 10.1%; omega -hydroxyacids 45.0, 48.1%; alkanols 1.9, 1.8%; 9,10-epoxy-18-hydroxyoctadecanoic acid 5.9 , 5.8%; 9,10-epoxyoctadecanodioic acid 4.8, 3.6%; 9,10,18-trihydroxyoctadec anoic acid 7.5, 10.4%; 9,10-dihydroxyoctadecanedioic 6.1, 6.8%; ferulic aci d 5.8, 4.5% and glycerol 4.3, 4.3%. In general, larger variability was foun d for the suberin monomers in virgin cork. Total content of omega -hydroxya cids or of C18 or C22 compounds is however similar for all samples. (C) 200 1 Elsevier Science B.V. All rights reserved.