Polyphenolic Compounds and Antimicrobial Activity of Quercus aucheri Leaves

Authors: MAHMUT KORAY SAKAR, DİDEM ŞÖHRETOĞLU, MERAL ÖZALP, MELİKE EKİZOĞLU, SONIA PIACENTE, COSIMO PIZZA

Abstract: Chromatographic studies (CC, VLC, MPLC, and PTLC) on ethyl acetate extract from the leaves of Quercus aucheri yielded 2 flavonoids (quercetin 3-O-\alpha-L-arabinopyranoside (1), quercetin 3-O-\beta-D-galactopyranoside (2)) and 2 tannin precursors and a procyanidin [(isolated as peracetates of (+)-catechin (3a), (+)-gallocatechin (4a) and epicatechin-(4\beta \to 8)-catechin (5a))]. The structures of the compounds were elucidated by UV, 1D-NMR (^1H, ^{13}C, TOCSY) and 2D-NMR (COSY, HSQC, HMBC) techniques. Different extracts (80% MeOH, EtOAc, n-BuOH and H_2O) from the leaves of Q. aucheri were investigated for their antimicrobial activity against 2 Gram-positive and 2 Gram-negative bacteria and 3 yeast-like fungi by a broth microdilution method. EtOAc extract, which showed the highest antimicrobial activity, was further used for isolation.

Keywords: Quercus aucheri, flavonol glycosides, (+)-catechin, (+)-gallocatechin, epicatechin-(4\beta \to 8)-catechin, antimicrobial activity

Full Text: PDF