Quantitative analysis of polymeric procyanidins (tannins) from grape (Vitis vinifera) seeds by reverse phase high performance liquid chromatography

A reverse phase C-18 HPLC method with potential for high automated throughp ut has been developed for the quantitative analysis of polymeric procyanidi ns (tannins)in grape seed extracts. Chromatography gave rise to 13 distinct W-absorbing peaks with good baseline separation. The UV-absorbing peak elu ting last is distinct and therefore easily quantified. Biochemical analyses including ultrafiltration, protein precipitation, and Sephadex LH20 chroma tography combined with electrospray mass spectrometric analyses establish t hat this peak predominantly contains polymeric procyanidins. The polymers, which appear to be galloylated to various degrees and seem to fragment in a characteristic manner during electrospray mass spectrometry, are well sepa rated from catechins and procyanidin oligomers of up to 4 units. The recove ry of polymeric grape seed tannins with this HPLC method was 86%, which is similar to the 89% recovery achieved with commercial quebracho tannins. The concentration of tannins in seeds from ripe Vitis vinifera cv. Shiraz grap es ranged from 1360 to 2830 mg/kg of berries.