Glyceryl-acyl and aryl-acyl dimers in Pseudotsuga menziesii bark suberin

The cork from the outer bark of Douglas-fir (Pseudotsuga menziesii) was exh austively extracted and submitted to a mild CaO-catalyzed methanolic depoly merization. The solubilized material (2.5 % yield) was derivatized and anal ysed with GC-MS. Glycerol was the main component (41.2%), followed by aliph atic acid monomers (30.6 %) and glyceryl and feruloyl dimers (14.5 %). Mono acylglyceryl eaters of alpha,omega-diacids were dominant (68% of glyceryl d imers), followed by monoacylglyceryl esters of alkanoic acids and of omega- hydroxyacids (respectively 20% and 9%). For all cases 1- and 2-monoacylglyc eryl esters were present. Dimers of w-hydroxyacids esterified to ferulic ac id through their primary hydroxyl were also found. The feruloyl ester of do cosanol could also be identified. The relative abundance of the dimers foll owed the proportion of acid monomers. The direct evidence found here for P. menziesii, and previously for Q. suber, that glycerol is esterified to all suberinic acids and that omega-hydroxyacids are esterified to ferulic acid supported the discussion of a suberin structure developing on glyceryl-dia cyl-glyceryl and glyceryl-hydroxyacyl-feruloyl backbones.