Condensed Tannins: (4β→8;2β→O→7) -Linked Procyanidins in Arachis hypogea L

Abstract

Mature, red peanut skins contain about 17% by weight of procyanidins. Nearly 50% of these compounds are low molecular weight oligomers that are soluble in ethyl acetate. The flavan-3-ols catechin and epicatechin are present in a ratio of 9 to 1 but in low concentration. Among the dimeric procyanidins, epicatechin-(4β→8;2β→O→7)-catechin dominates, with smaller proportions of epicatechin-(4β→8;2β→O→7)-epicatechin and very small proportions of epicatechin-(4β→8)-catechin. Higher oligomers that are soluble in ethyl acetate contain both the (4β→8;2β→O→7) and (4β→8;2β→O→7) interflavanoid bonds. The water-soluble polymeric procyanidins are predominately 2,3-cis-procyanidins linked by (4β→8;2β→O→7) bonds that are terminated with the 2,3-trans-flavan-3-ol catechin. Water-soluble polymeric procyanidins from flaked and pelletized peanut skins have comparatively low number-average molecular weights (about 2200 as the peracetate) and low dispersitivities (about 1.8). These polymers have excellent potential for use in cold-setting adhesive applications. © 1986, American Chemical Society. All rights reserved.