PROCYANIDIN DIMERS AND TRIMERS FROM GRAPE SEEDS

Fractionation of a grape (Vitis vinifera) seed extract yielded various natural procyanidin dimers and trimers isolated and identified for the first time in grapes: procyanidin dimers B5 [epicatechin-(4-beta-->6)-epicatechin], B6 [catechin-(4-alpha-->6)-catechin] and B8 [catechin-(4-alpha-->6)-epicatechin]; four procyanidin trimers [epicatechin-(4-beta-->6)-epicatechin-(4-beta-->8)-epicatechin], [epicatechin-(4-beta-->8)-epicatechin-(4-beta-->6)-catechin], [epicatechin-(4-beta-->8)-epicatechin-(4-beta-->6)-epicatechin], [epicatechin-(4-beta-->6)-epicatechin-(4-beta-->8)-catechin] along with five galloyl procyanidins: B2 3-O-gallate, B1 3-O-gallate, B4 3'-O-gallate, B2 3,3'-di-O-gallate and [epicatechin-(4-beta-->8)-epicatechin 3-O-gallate-(4-beta-->8)-catechin]. The presence of (+)-catechin, (-)-epicatechin, (-)-epicatechin 3-O-gallate, procyanidins dimers B1, B2, B3, B4, B7, B2 3'-O-gallate and procyanidin trimers C1 and [epicatechin-(4-beta-->8)-epicatechin-(4-beta-->8)-catechin] was also confirmed. The structures of all these compounds were elucidated by enzymatic hydrolysis, complete acid hydrolysis, partial acid-catalysed degradation with phloroglucinol and phenylmethanethiol, FABMS and H-1 NMR. Separation of procyanidins and of their phloroglucinol or phenylmethanethiol adducts was achieved by TLC on silica plates and HPLC.