Biomedical subjects

José Graça

Publications and source records attributed to José Graça.

3 recordsLinked to original sources

PubMed2006

Glycerol-derived ester oligomers from cork suberin.

The cork suberin polyester was partially depolymerized by a methanolysis reaction catalyzed by calcium hydroxide. The methanolisate was analysed by ESI-MS/MS in the form of [M+Li](+) adduct-ions. This reaction solubilized a mixture of monomers and oligomers, including a set of glycerol-derived dimeric and trimeric esters. Four types of glycerol esters were identified: monoacylglycerols of alpha,omega-diacids, of omega-hydroxyacids and of monoacids; diglycerol diesters of alpha,omega-diacids; diacylglycerols of alpha,omega-diacids; monoacylglycerols of linear dimeric esters of alpha,omega-diacids and omega-hydroxyacids. The alpha,omega-diacids and omega-hydroxyacids found as monomer residues in the glycerol esters are the main ones found as cork suberin monomers. It is concluded that suberin is a glycerol-derived lipid of polymeric dimensions. Due to the protective and insulating role that it plays in plants, suberin should be considered together with the other known glycerolipids that build up biological membranes.

Dimerization↗

PubMed2006

Linear aliphatic dimeric esters from cork suberin.

Cork suberin was partially depolymerized by methanolysis catalyzed by calcium hydroxide. Analysis by GC-MS of the methanolysate showed suberin monomers, including glycerol and long-chain alpha,omega-diacids and omega-hydroxyacids. ESI-MS analysis of the methanolysate showed, besides the aliphatic monomers, suberin oligomers, including linear dimeric esters of alpha,omega-diacids and omega-hydroxyacids. Two types of dimeric esters were identified: a alpha,omega-diacid linked to a omega-hydroxyacid and two inter-linked omega-hydroxyacids. The alpha,omega-diacids and omega-hydroxyacids found as monomer residues in the dimeric esters were mainly the C18 monomers with midchain substituents. The identification of these dimeric esters was based in their CID-MS/MS spectra and confirmed after synthesis of model compounds. The occurrence of inter-esterified long-chain monomers in suberin brings a new insight in the understanding of the polyester structure of this biopolymer.

Dimerization↗

PubMed2002

Glycerol and glyceryl esters of omega-hydroxyacids in cutins.

Cutins from the leaves and fruits of seven plant species were depolymerized by NaOCH(3)-methanolysis. The monomers that were released mostly included C16 and C18 omega-hydroxyacids with mid-chain oxygenated substitutions, namely epoxy and hydroxyl groups. Glycerol was also solubilized as a monomer in quantities that ranged from 1 to 14% of the methanolysates. Partial depolymerization of three cutins by CaO-methanolysis released the same monomers as had been obtained in the previous reaction, as well as small quantities of 1- and 2-monoacylglyceryl esters of omega-hydroxyacids. Molar proportions of glycerol permit the esterification of a significant part of the aliphatic omega-hydroxyacids, thereby possibly playing a major role in the polyester structure of cutin. Glycerol had not previously been known to form part of the cutin polymer.

Esters↗