Isolation and structure elucidation of tetrameric procyanidins from unripe apples (Malus pumila cv. Fuji) by NMR spectroscopy

► Procyanidins from apple were fractionated according to their degree of polymerization. ► Eleven compounds were detected as tetrameric procyanidins and all of them were isolated. ► The structures of nine unknown tetramers were elucidated by NMR and phloroglucinol degradation.