Isolation and Identification of Triglycerides and Ester Oligomers from Partial Degradation of Potato Suberin

Abstract

Suberized cell walls from wound-healing potato tubers (Solanum tuberosum) were depolymerized under mild conditions using methanolic potassium hydroxide in order to investigate the chemical linkages present in this protective plant biopolymer. Analysis of the resulting soluble oligomeric fragments with HPLC, 1D and 2D NMR, LC/MS and MSn methods allowed identification of several novel compounds: a family of homologous triglycerides, a family of homologous aliphatic ester trimers, and an ether linked phenylacetic acid dimer. These findings illustrate the diversity of rigid and flexible molecular linkages present in both poly(aliphatic) and poly(aromatic) domains of potato suberin, and they point toward architectures that may account for its function as a potent hydrophobic barrier to water, thermal equilibration, and microbial pathogens.

Partial depolymerization of genetically modified potato tuber periderm reveals intermolecular linkages in suberin polyester

“…Finally, the main x-hydroxyacids, C18:1 and C16, were also observed in the form of ferulates. A number of triacylglycerols have already been found in the partially depolymerized (by a mild alkaline hydrolysis) suberin of wound periderm in potatoes, but they included as acyl moieties mostly short chain aliphatic monoacids, or otherwise unknown acids as typical monomers of potato periderm suberin (Wang et al, 2010).…”

“…In this way dimeric and trimeric esters, comprising as residues glycerol, long-chain x-hydroxyacids and a,x-diacids, and ferulic acid, were found in potato periderm (Graça and Pereira, 2000), and cork suberins (Graça and Santos, 2006a). The partial degradation of wound potato suberin by hydrolysis also released oligomers including triacylglycerols, a trimeric aliphatic ester, aromatic acids bridged by an aliphatic ether (Wang et al, 2010), and ferulic acid esterified to aliphatics (Arrieta-Baez and Stark, 2006). The insight brought by the oligomer structures solubilized from suberin led to a working model for the suberin macromolecule (Graça and Santos, 2007).…”

“…Conceivable as ''molecule sequencing'' another approach for the study of the suberin macromolecule has been its partial depolymerization, by chemical or enzymatic methods, and the structural analysis of the ensuing soluble oligomers by mass spectrometry (Graça and Pereira, 1997;Rocha et al, 2001;Wang et al, 2010). In this way dimeric and trimeric esters, comprising as residues glycerol, long-chain x-hydroxyacids and a,x-diacids, and ferulic acid, were found in potato periderm (Graça and Pereira, 2000), and cork suberins (Graça and Santos, 2006a).…”

Chemical composition and antioxidant activity of extracts from Erythroxylum suberosum A.St. Hil.leaves

“…Total flavonoid contents in crude extract and fractions were determined according to the method of Woisky and Salatino (1998), with modifications (Buriol, et al, 2009;Woisky and Salatino, 1998). To 250 µL of sample solutions at a concentration of 2000 µg/mL in methanol, 125 µL AlCl 3 5% methanol solution was added, and the volume was completed for 2500 µL with distilled water and mixed.…”

“…The fractionation of the hexane extract (EH) of E. Suberosum leaves led to the isolation and structural identification of a mixture of long chain aliphatic esters by 1 H and 13 C NMR and comparison with literature data (Wang, et al, 2010). Compound 1 was isolated from the aqueous extract by repeated CC on Sephadex LH-20 and analyzed by TLC and NMR techniques.…”