Relative abundances of novel cyclic prodelphinidins in wine depending on the grape variety.

The identification of cyclic B-type procyanidins in grape and wine was recently disclosed. Some of these were also found in berries of totally different vegetal species (e.g. Vaccinium sp.). However, presence of a wider class of these cyclic condensed tannin compounds with variably substituted monomers has never been addressed so far. Here, an extended list of oligomeric cyclic proanthocyanidins (PAC) bearing variable substitution patterns on the main flavan-3-ol unit has been searched in wines. Nearly 7,600 theoretical structures were calculated and searched in red and white wine samples made from different grape varieties. Moreover, an hydrogen/deuterium exchange approach (already applied to a cyclic tetrameric procyanidin) coupled to high-resolution mass spectrometry was applied to confirm their cyclic B-type structure rather than a non-cyclic A-type structure, otherwise isomeric and undistinguishable by LC-MS alone. The main group of novel cyclic PAC observed is shown to contain (epi) gallocatechin beside (epi) catechin as the constituent monomers.