title: Proanthocyanidins from Quercus petraea Bark.
abstract: Flavanols and oligomeric proantho-cyanidins were isolated from oak bark ( QUERCUS PETRAEA) and characterized by acid hydrolysis, gel permeation chromatography, haemanalysis, and complete as well as partial thiolytic degradation. The proantho-cyanidins had an average polymerization degree of 6.1 and a procyanidin: prodelphinidin ratio of 6:4. The prevailing units of the oligomeric chains were (+)-catechin, (-)-epicatechin, and (+)-gallocatechin, minor units were (-)-epicatechin 3- O-gallate and (-)-epigallocatechin 3- O-gallate. The bark contains both hydrolyzable and condensed tannins. Although only 23% of the water-soluble oak bark tannins consisted of oligomeric proanthocyanidins, these contributed with 55% to the astringency of the total tannin fraction.
authors.affiliation: Institut für Pharmazeutische Biologie, Schänzlestraße 1, D(W)-7800 Freiburg, Federal Republic of Germany.
authors.forename: E
authors.initials: E
authors.lastname: Pallenbach
authors.forename: E
authors.initials: E
authors.lastname: Scholz
authors.forename: M
authors.initials: M
authors.lastname: König
authors.forename: H
authors.initials: H
authors.lastname: Rimpler