Proanthocyanidin glycosides from the leaves of Quercus ilex L. (Fagaceae)

From the polar extracts of the leaves of Quercus ilex L., two new proanthocyanidin glycosides, namely afzelechin-(4 alpha -> 8)-catechin-3-O-beta-glucopyranoside (1) and afzelechin-(4 alpha -> 8)-catechin-3-O-alpha-rhamnopyranoside (2). were isolated in addition to catechin (3), proanthocyanidin B(3) (4). prodelphinidin C (5), dehydrodicatechin A (6), quercetin (7) and six known flavonol glucosides with their acylated derivatives (8-13) and ellagic acid (14). The structures of all isolated compounds were established by spectroscopic means, mainly 1D and 2D NMR, as well as LC/MS and HR-MS spectrometric analyses. The absolute configuration of compound I was determined by CD measurements. The proanthocyanidin glycosides are especially interesting, as they possess the sugar in the upper unit of the dimer, which is rare for this type of compounds. (C) 2009 Elsevier Ltd. All rights reserved.