Analysis of commercial proanthocyanidins. Part 1: The chemical composition of quebracho (Schinopsis lorentzii and Schinopsis balansae) heartwood extract

► Mass spectrometry investigation into the proanthocyanidins in commercial quebracho extract. ► Extract does not contain detectable quantities of robinetinidol as monomer or as part of an oligomer. ► The starter unit in our sample was thus always catechin and the extender units always ent-fisitinedol. ► Quebracho extract consists of 33% dimers, 37% trimers, 21% tetramers, 8% pentamers, and 1% heptamers. ► A degree of polimerization of 3.1 was calculated from the intensity of MS fragments.