Polymeric Proanthocyanidins from the Bark of Hamamelis virginiana

Abstract

Polymeric proanthocyanidins were isolated from the bark of Hamamelis virginiana L. in yields of about 5 %. Fractionation yielded fractions with similar structures but different molecular weights with DP between 17 - 29 (thiolysis) and 11 - 20 (GPC). Polymers were composed predominantly of epicatechin and epigallocatechin as chain extension units at ratio of about 1.3 : 1. Terminal chain units were catechin (∼ 95 %) and gallocatechin (∼ 5 %). All chain extension units were completely galloylated at position O-3, while chain terminating units were not galloylated. Predominant interflavan linkages were 4 → 8-bonds.

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