Dimeric procyanidins: screening for B1 to B8 and semisynthetic preparation of B3, B4, B6, And B8 from a polymeric procyanidin fraction of white willow bark (Salix alba).
Fifty-seven samples have been analyzed with regard to the occurrence of dimeric procyanidins B1-B8 as well as the composition of polymeric procyanidins. Fifty-two samples were found to contain polymeric procyanidins. In most of the samples, (-)-epicatechin was the predominant unit present. In white willow bark (Salix alba), however, large amounts of (+)-catechin (81.0%) were determined by means of phloroglucinolysis. White willow bark has therefore been used for the semisynthetic formation of dimeric procyanidins B3 [(+)-C-4alpha --> 8-(+)-C)], B4 [(+)-C-4alpha --> 8-(-)-EC)], B6 [(+)-C-4alpha --> 6-(+)-C)], and B8 [(+)-C-4alpha --> 6-(-)-EC)]. The reaction mixtures of the semisynthesis were successfully fractionated with high-speed countercurrent chromatography (HSCCC), and dimeric procyanidins B3, B4, B6, and B8 were obtained on a preparative scale.
Esatbeyoglu
Tuba
T
Institute of Food Chemistry, Technische Universität Braunschweig, Schleinitzstrasse 20, 38106 Braunschweig, Germany.
Wray
Victor
V
Winterhalter
Peter
P
D019281:Dimerization; D024301:Plant Bark / Q000737:chemistry*; D010936:Plant Extracts / Q000138:chemical synthesis / Q000737:chemistry*; D044945:Proanthocyanidins / Q000138:chemical synthesis / Q000737:chemistry*; D032108:Salix / Q000737:chemistry*
D010936:Plant Extracts; D044945:Proanthocyanidins