Isolation and Structural Characterization of Refined Proanthocyanidin Fractions Reveal Polymerization and Prodelphinidin Ratio as Major Contributors to Antiparasitic Activity.

Proanthocyanidins are a highly bioactive group of plant-specialized metabolites. The aim of this study was to investigate the antiparasitic activity of a comprehensive set of highly purified and characterized proanthocyanidin fractions with versatile procyanidin/prodelphinidin ratios, mean degrees of polymerization, and galloyl contents. In total, 111 characterized fractions from 11 plant species were tested against the parasitic nematode Ascaris suum using migration inhibition and mortality assays. The results showed that a high mean degree of polymerization and a high proportion of prodelphinidins increased the antiparasitic activity of the fractions. The galloylated proanthocyanidin fractions did not possess especially high antiparasitic activity because of their low mean degree of polymerization. In general, highly procyanidin-rich fractions had low activity, yet there were significant differences in activity among fractions, which consisted mainly of A-type proanthocyanidins and those, which consisted mainly of B-type proanthocyanidins.