An improved method for thiolysis-HPLC characterization of grape seed procyanidins

摘要

Polymeric procyanidins (PAs) of grape seeds play a fundamental role in determining healthy and sensory characteristics of grape products. Both, wine organoleptic properties and biological effects depend on structural units and average molecular weight of these grape metabolites. In this paper a unique solid phase extraction step of purification was performed to obtain a series of fractions submitted to the reverse phase HPLC analysis after acid catalized degradation in the presence of toluene-a-thiol. The analysis was performed on the extract obtained from Primitivo grape seeds (from Apulia region in the South of Italy) and the resin used for the preparative step was the Toyopearl TSK HW-50 (F). A total of ten purified fractions were obtained and characterized by reverse-phase HPLC following thiolysis. The compounds with highest degree of polymerization detected in the extract were heptamers. The mean degree of polymerization (DPm) was 3,2 and an increase of the percentage of galloylation with the degree of polymerization was observed. Therefore in this study the careful manipulation of the solid phase extraction step gave a suitable and useful method for the analysis of PAs.