Quercus suber

P.J. Holloway, Composition of suberin from the corks of Quercus suber and Betula pendula, Chemistry and Physics of Lipids, 9, 158 170 (1972). 

Rudnitskaya, A., Delgadillo, I., Rocha, S. M., Costa, A.-M., and begin, A. (2006a). Quality evaluation of cork from Quercus suber L. by the electronic tongue. Anal. Chim. Acta 563 (1-2), 315-318. 

Cork from the cork-oak (Quercus suber L.) differs chemically from wood, mostly by the presence of suberin as a major structural component (ca. 60% of extractive free cork) in addition to lignin and polysaccharides (6).The structure of suberin is not fully elucidated yet. It is a cross-linked polymer with a polyester linked aliphatic domain containing fatty acids, alcohols, hydroxyacids and diacids and a phenolic, probably lignin-like domain. 

Cork from cork-oak (Quercus suber L.) was collected in a mill as residue obtained from the production of stoppers and a 40-60 mesh fraction was separated. This fraction was exhaustively extracted with dichloromethane, ethanol and water in a Soxhlet apparatus. High-pressure extractions were performed upon extractive -free anhydrous cork samples. 

Friedelin (friedelane triterpene) Ceratopetalum petalum (Cunoniaceae), Quercus suber (Fagaceae) [cork], Viola odorata (Violaceae), lichens PKA... 

Cork stoppers are manufactured from the outer bark (suberose parenchyma) of the cork oak, Quercus suber L. 16). The cork oak is grown in several Mediterranean countries, with Portugal accounting for more than half of the world-wide production of cork (ca. 170,000 t on average) and about 78% of bark wine bottle stoppers (18 billion/year). Starting out with a planted acorn, it takes, even under ideal conditions. 

Quercus suber (Cupuli ferae) Italy Quercus cerris (Cupuliferae) Italy... 

KHENNOUF, S., BENABDALLAH, H., GHARZOULI, K., AMIRA, S., ITO, H., KIM, T. H., YOSHIDA, T., GHARZOULI, A., Effect of tannins from Quercus suber and Quercus coccifera leaves on ethanol-induced gastric lesions in mice, J. Agric. Food Chem., 2003, 51, 1469-1473. 

C30H30O, Mr 426.73, needles, mp. 267-269 °C, [aJu -27.8 (CHCI3). A pentacyclic " triterpene widely distributed in many higher plants and lichens it can be obtained as the main component from the cork of the cork oak (Quercus suber, Fagaceae) by extraction with hot ethanol. F. has diuretic activity. 

Synonyms Oak cork Quercus occidentalis Quercus suber... 

Definition From Quercus suber or Q. occidentaiis Uses Natural flavoring agent in alcoholic beverages... 

The other macromolecule found only in certain wood species is suberin. This non-linear polyester contains very long aliphatic moieties which impart a characteristic hydrophobic feature to the natural material that contains it. Figure 1.7 shows a schematic structure of suberin. By far the most representative species containing this polymer in its very thick bark (the well-known cork) is Quercus suber, which grows in the Mediterranean area, but Nordic woods like birch, also have a thin film of suberin coating their trunks. The sources of suberin, as well as the corresponding structure and composition are described in Chapter 14, together with the use of its monomeric components for the synthesis of novel macromolecular materials. 

Quercus suber, Betula pendula, Cork, Suherin, Chemical composition. Aliphatic macromonomers. Polyurethanes, Polyesters... 

Despite being widespread in plants [1], only two species produce suberin-rich biomass residues in amounts that justify their exploitation as renewable sources of chemicals for polymer synthesis, namely Quercus suber with cork and Betula pendula (birch) with its outer bark. Quercus suber cork is a mataial with unique properties and applications, whereas to the best of our knowledge, the outer bark of birch finds no direct applications. 

Among the countries involved in the cultivation of Quercus suber and the production of cork, Portugal is largely the leader with an annual production of 185000 ton, which constitutes about 50 per cent of the world output [4]. Although Quercus suber is a protected species and a key element in the southern Portugal ecosystem and landscape, cork exploitation is a fully sustainable activity, if adequately carried out by professionals. Indeed, cork stripping which is carried out once every 9-12 years seems to have a positive effect on the tree s health and growth. 

As mentioned above, and despite the fact that suberin is widespread in plants [1], only two species produce suberin-rich biomass residues in amounts that justify the exploitation of this natural polyester as a renewable source of chemicals for polymer synthesis, namely, Quercus suber and Betula pendula. Betula pendula is one of the most important industrial hardwood species in Northern Europe, where it is mainly used as raw material in the pulp and paper industry, which generates considerable amounts of bark. Typically, a mill with a pulp production of 400 000 ton per year, leaves about 28000 ton per year of outer bark [37]. Considering a suberin content ranging from 32 to 59 per cent, [14], birch s outer bark has, like cork, an enormous potential as a source of suberin and suberin components. 

The detailed monomer distribution of suberin from several species has been recently reviewed [14]. Table 14.1 summarizes the composition of the two most relevant suberin sources in the present context i.e. Quercus suber cork and Betula pendula outer bark) and the structures of representative elements of each group are shown in Fig. 14.4. 

Relative abundance of aliphatic suberin monomers from the extractive-free Quercus suber cork and Betulapendula outer bark (adapted from [14])... 

The only suherin depol5mierization mixtures which were reported to have been used for functional characterization and for the synthesis of polymeric materials were obtained from Quercus suber cork, with the exception of a recent study where the reactive monomer was isolated from birch outer bark suberin [75]. 

The only thorough characterization of mixtures of depolymerized suberin components (dep-suberin) was carried out by us in a comprehensive investigation of this material. The opaque pasty samples were obtained by the alkaline methanolysis of Quercus suber L. cork [8,76]. Under the conditions used for the depolymerization, most of the carboxylic acid functions were therefore converted into the corresponding methyl esters. 

Conde E., Cadahia E., Garcia-Vallejo M.C., Gonzalez-Adrados J.R., Chemical characterization of reproduction cork from Spanish Quercus suber, J. Wood Chem. TechnoL, 18(4), 1998, 447—469. 

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