Compositional Analysis of Polymeric Proanthocyanidins from Vitis amurensis Rupr. (Vitaceae) Seeds After Catechin-Assisted Sulfitolytic Cleavage

Polymeric procyanidins (PPCs) constitute the major fraction of procyanidins, but they have poor bioactivity. The purpose of this study is to clarify the composition and content of PPCs from Vitis amurensis Rupr. (Vitaceae) seeds before and after depolymerization, thereby providing a theoretical basis for activity evaluation and application of proanthocyanidins (PCs). PPCs extracted from V. amurensis seeds were depolymerized by catechin-assisted sulfitation. The compositions and contents of PCs before and after depolymerization were qualitatively and quantitatively analyzed by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS), high-performance liquid chromatography (HPLC), and liquid chromatography–tandem mass spectrometry (LC-MS/MS). Results showed that twenty-eight components were identified (7 monomers, 13 dimers, 5 trimers, 1 tetramer and 2 unknowns). Before depolymerization, tetrameric and higher polymers dominated, accounting for 58.81% of the relative content. After depolymerization, these high-molecular-weight compounds declined to <1% or became undetectable, while monomers and dimers (with minor trimers) surged to 42.89%. Among them, the relative content of two monomers and three dimers, catechin, epicatechin gallate and procyanidin B1–B3, increased by 37.00, 3.75, 10.98, 3.72 and 9.74 times, respectively. In conclusion, the method utilizing catechin-assisted sulfitation effectively depolymerizes PPCs from V. amurensis seeds into oligomeric components such as monomers and dimers.