POLYMERIC PROANTHOCYANIDINS FROM GRAPE SKINS

LC-mass spectrometric analysis of the degradation products released by thioacidolysis of a grape (Vitis vinifera var. Merlot) skin extract s howed that catechin, epicatechin, epicatechin;gallate and epigallocate chin were the major constitutive units of grape skin tannins. Gallocat echin and epigallocatechin gallate were also detected. Epicatechin rep resented 60% of the extension units, whereas 67% of the terminal units consisted of catechin. Six fractions were prepared from the skin tann in extract by normal phase and analysed by reverse-phase HPLC after th ioacidolysis. The mean degree of polymerization (mDP) calculated for e ach fraction ranged from three (in fraction I) to 80 (in fraction VI), confirming that proanthocyanidins were eluted from the normal phase c olumn in increasing order of M(r). All fractions contained prodelphini dins. The proportion of galloyllated units was low (3% to 6%) and inde pendent of mDP. Copyright (C) 1996 Elsevier Science Ltd