A reverse phase C18 HPLC method with potential for high automated throughput has been developed
for the quantitative analysis of polymeric procyanidins (tannins) in grape seed extracts. Chromatography
gave rise to 13 distinct UV-absorbing peaks with good baseline separation. The
UV-absorbing peak eluting last is distinct and therefore easily quantified. Biochemical analyses
including ultrafiltration, protein precipitation, and Sephadex LH20 chromatography combined with
electrospray mass spectrometric analyses establish that 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 separated from catechins
and procyanidin oligomers of up to 4 units. The recovery 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 grapes ranged
from 1360 to 2830 mg/kg of berries.