RESUMEN
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.