title: Salix daphnoides: A Screening for Oligomeric and Polymeric Proanthocyanidins.
abstract: In the present study, a qualitative analysis of proanthocyanidins (PAs) from an aqueous-methanolic extract of Salix daphnoides VILL. bark is described. Procyanidin B1 (1), B2 (2), B3 (3), B4 (4), C1 (5), epicatechin-(4β→8)-epicatechin-(4β→8)-catechin (6) and epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin-(4β→8)-catechin (7) have been isolated by a combination of different chromatographic separations on Sephadex® LH-20-, MCI®-, Diol-and RP-18-phases. Mass spectrometry, 1D- and 2D-NMR, circular dichroism and polarimetry were used for their structure elucidation and verification by comparison with the literature. Additionally, two fractions of very polar flavan-3-ols were compared: "regular" polymeric PAs received at the very end of the Sephadex® LH-20 chromatography showing no mobility on silica TLC and "unusual" PAs with the same RF-value but already eluting together with flavonoids in the Sephadex® LH-20 system. These "unusual" PAs were subsequently enriched by centrifugal partition chromatography (CPC). 13C-NMR, polarimetry, thiolysis, acid hydrolysis and phloroglucinol degradation were used to characterize both fractions. Differences in the composition of different flavan-3-ol units and the middle chain length were observed.
authors.affiliation: Institute of Pharmaceutical Biology, Universitätsstr. 31, Regensburg D-93053, Germany. guido.juergenliemk@chemie.uni-regensburg.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wiesneth
authors.affiliation: Institute of Pharmaceutical Biology and Phytochemistry (IPBP), Corrensstr. 48, Münster D-48149, Germany. frank.petereit@uni-muenster.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Petereit
authors.affiliation: Institute of Pharmaceutical Biology, Universitätsstr. 31, Regensburg D-93053, Germany. guido.juergenliemk@chemie.uni-regensburg.de.
authors.forename: Guido
authors.initials: G
authors.lastname: Jürgenliemk
mesh_terms: D015394:Molecular Structure; D044945:Proanthocyanidins / Q000737:chemistry*; D032108:Salix / Q000737:chemistry*
chemical_list: D044945:Proanthocyanidins; C013221:proanthocyanidin
keywords: Salix daphnoides; flavan-3-ols; low temperature NMR; polarimetry; polymeric proanthocyanidins; proanthocyanidins; procyanidins; thiolysis; willow bark