Résumé
Objective The oligomeric and polymeric proanthocyanidins in different fractions from Hippophae rhamnoides seeds were investigated. Methods The monomeric and oligomeric fractions were analyzed by HPLC/ESI-MASS detection. The polymeric proanthocyanidins were fractionated by Sephadex LH-20 column chromatography and their chemical constructures were studied by acid-catalysed degradation in the presence of benzyl mercaptan. Results Four monomers were identified as catechin, epicatechin, gallocatechin, and epigallocatechin. Eight dimers including three dimeric procyanidins and one dimeric prodelphinidin, and four mixed dimers were detected and their structures were partly elucidated by the detection of the pseudomolecular ion and main ion fragmentations. The results also showed that polymers to be highly heterogenous with catechin, epicatechin, gallocatechin, and epigallocatechin all being components of both the extension and the terminal units. The extension units were mainly gallocatechin, whereas the terminal units were mainly gallocatechin and epigallocatechin for all fractions. The proanthocyanidins with a mean degree of polymerization (mDP) of 9.1, 13.2 and 17.0 represented the three major polymeric fractions. Conclusion Proanthocyanidins of H. rhamnoides seeds, predominantly being of prodelphinidin-type, are remarkably different from that of grape seeds.
Résumé
Object The analysis of oligomeric procyanidins in crude grape seed extracts was performed by reversed-phase high-performance liquid chromatography with electrospray ionization mass spectrometry (RP-HPLC/ESI-MS). Methods Procyanidin monomer and oligomers were identified according to the mass of the charged pseudomolecular ion [M-H]. Results Three monomers, seven dimmers and three trimers were tentatively identified. Conclusion This study demonstrates the capability of the combination of RP-HPLC with ESI-MS to analyze the composition of oligomeric procyanidins in grape seed extracts.