Suberin extraction from bark

Compounds which fit the broad definition of wax have been found in extracts of suberin-rich barks (Martin and Juniper, 1970). The wax associated with suberin, because of its physical location, cannot be as readily removed as cuticular wax, and therefore the exact location of the extracted wax is not clear. However, it seems likely that a major portion of the waxes extracted from barks are associated with the polymeric material suberin. 

Cuticular waxes are removed from surface layers of intact tissues by washing with organic solvents such as hexane or chloroform. It is very important to use redistilled solvents particularly since compounds such as hydrocarbons are natural components of most waxes. Internal waxes are extracted from tissues following homogenization by the usual methods (Section 6.3.1). Waxes have also been extracted from suberin-rich barks (Martin and Juniper, 1970). 

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

Waxes are usually isolated by extracting the tissue with a nonpolar solvent such as chloroform or hexane. Cuticular waxes can be extracted by a quick dip into the solvent at room temperature, but suberin-associated waxes are more difficult to remove because they are embedded in the suberized cell wall (232). Wax from the suberized cells of bark has to be isolated by Soxhlet extraction of dried and powdered tissue to assure its complete removal. Isolated wax can be subjected to GC/MS analysis either after separation into various classes by thin-layer or column chromatography or directly after derivitization of the functional groups (232, 253, 459, 460). 

The phenolic domain of the suberin polymer has not been well characterized. Early chemical studies on suberin from tree bark indicated that the polymer contains phenolics. Suberin from the cork of Pseudotsuga menziesii bark released phenolic acids (43% of extractive-free cork) and aliphatic acids (35%) upon saponification (180). Suberin, which was subjected to a limited saponification (2% KOH at room temperature) and successive solvent extraction with hexane. 

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