Suberin Structure in Potato Periderm:  Glycerol, Long-Chain Monomers, and Glyceryl and Feruloyl Dimers

Suberin in extractive-free potato periderm amounts to approximately 25% determined by NaOCH(3) methanolysis. Monomeric composition is characterized by glycerol (20% of monomers), long-chain alpha, omega-diacids, omega-hydroxyacids, alkanoic acids, and alkan-1-ols, with predominance of octadec-9-enodioic acid and 18-hydroxyoctadec-9-enoic acid (39 and 15% of long-chain monomers, respectively). Aromatic hydroxycinnamyl monomers were also present (<1%). Partial depolymerization of potato periderm suberin using a Ca(OH)(2)-catalyzed methanolysis solubilized approximately 10% of suberin aliphatics. GC-MS analysis showed the presence of monomers, dimers, and trimers (87, 12, and 1% of identified compounds, respectively). A total of 26 dimers were identified by EIMS: monoacylglyceryl esters of alpha,omega-diacids, omega-hydroxyacids, and alkanoic acids (with predominance of the 1- and 2-isomers of the monoacylglyceryl ester of the octadec-9-enodioic acid), as well as feruloyl esters of omega-hydroxyacids and alkan-1-ols and a small quantity of a monoferuloylglycerol. Following a discussion of suberin macromolecular structure, it is proposed that in suberized cell walls, the polyaliphatic polymers have a three-dimensional development ensured by glycerol and exist independently from the associated polyaromatics.