Phenolic Extractives in Southern Red Oak Bark

The bark of southern red oak (Quercus falcala Michx. var. falcala) is a rich source of quercitrin (quercetin3-rhamnoside). It contains only low concentrations of (+ )-catechin and no significant amounts of epicatechin or gallocatechin. The three major dimeric proanthocyanidins present are epicatechin(4f,>8)-catechin, catechin-(4a>8)-catechin and the 3-gallate ester of epicatechin-( 4~>8)-catechin. No biphenyl-linked dimeTS and no flavan-3-olor 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-lrans ( + )-catechin. The polymers contain only small amounts of 2,3-lrans 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.