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The phenolic extractives in southern red oak (Quercus falcata Michx. var. falcata)Author(s): Seiji Ohara; Richard W. Hemingway
Source: Holzforschung 43(3):149-154
Publication Series: Miscellaneous Publication
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DescriptionThe bark of southern red oak (Quercus falcala Michx. var. falcala) is a rich source of quercitrin (quercetin-3-rhamnoside). It contains only low concentrations of (+)-catechin and no significant amounts of epicatechin or gallocatechin. The three major dimeric proanthocyanidins present are epicatechin-(4β→8)-catechin, catechin-(4α→8)-catechin and the 3-gallate ester of epicatechin-(4β→8)-catechin. No biphenyl-linked dimers and no flavan-3-ol- or proanthocyanidin-glycosides are evident. The higher molecular weight acetone-water soluble tannins are polymeric procyanidins predominantly made up of 2,3-cis chain extender units and terminated with the 2,3-trans (+)-catechin. The polymers contain only small amounts of 2,3-trans procyanidins chain extender units and only traces of prodelphinidin units. Although a gallate ester of a dimer is present in significant amounts, neither gallate esters of higher molecular weight procyandins nor hydrolysable tannins are detectable through reaction products or IR and 13C-NMR spectral studies.
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CitationOhara, Seiji; Hemingway, Richard W. 1989. The phenolic extractives in southern red oak (Quercus falcata Michx. var. falcata). Holzforschung 43(3):149-154
KeywordsRed oak, bark, flavonoids, tannins, proanthocyanidins, gallate esters
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