Polyphenols from peanut skins and their free radical-scavenging effects

Separation of the water-soluble fraction of peanut skins led to the isolation of five proanthocyanidins. Based on the spectroscopic investigation and partial acid catalyzed degradation, their structures were determined to be epicatechin-(2beta --> O --> 4beta --> 6)-[epicatechin-(4beta --> 8)]-catechin (1), epicatechin-(2beta --> O --> 7, 4beta --> 8) epicatechin-(4beta --> 8)-catechin-(4alpha --> 8)-epicatechin (2), and procyanidins B2 (3), B3 (4) and B4 (5). The absolute configuration of the new compounds was determined from their circular dichroism curves and the H-1 NMR spectra of analysis of flavan-3-ols formed by thiolytic degradation of 1 and 2 in the presence of a chiral dirhodium complex (dirhodium tetra-(R)-(trifluoromethyl) phenyl acetate). (C) 2004 Elsevier Ltd. All rights reserved.