Analysis of commercial proanthocyanidins. Part 2: An electrospray mass spectrometry investigation into the chemical composition of sulfited quebracho (Schinopsis lorentzii and Schinopsis balansae) heartwood extract

► An ESI investigation into the composition of sulfited quebracho proanthocyanidins. ► Extraction with bisulfite leads to the introduction of sulfonic acid moieties. ► C-4 sulfitation breaks interflavanyl bonds and reduces chain length. ► C-2 sulfitation opens the pyran ring and increases water solubility. ► A chromatographic method to separate and quantify sulfited and non-sulfited PACs.