title: Polyphenols from Ginkgo biloba.
abstract: By Sephadex LH-20 gel chromatography of an extract from Gingko biloba leaves, polymeric proanthocyanidins were eluted after the fractions of flavonol glycosides and biflavone glycosides. A purified proanthocyanidin polymer accounted for 86.6% of the total proanthocyanidins, and for 37.7% of the total antioxidant activity of this leaf extract. For structure elucidation, the polymer was submitted to acidic depolymerization in the presence of phloroglucinol. The structures of the resulting flavan-3-ols and phloroglucinol adducts were determined on the basis of 1D-and reverse 2D-NMR (HSQC, HMBC) spectra of their peracetylated derivatives, MALDI-TOF-MS and CD-spectroscopy. The observations resulting from the degradation with phloroglucinol were confirmed by (13)C-NMR spectroscopy of the polymer. The mean molecular weight of the polymeric fraction was estimated to be 9â10 flavan-3-ol-units.
authors.affiliation: Faculty of Pharmacy, Petra University, Airport Street, P O Box 961343 Amman, Jordan. fqadan@gmail.com
authors.forename: Fadi
authors.initials: F
authors.lastname: Qaâdan
authors.forename: Adolf
authors.initials: A
authors.lastname: Nahrstedt
authors.forename: Mathias
authors.initials: M
authors.lastname: Schmidt
authors.forename: Kenza
authors.initials: K
authors.lastname: Mansoor