Structural identification of the main ellagitannins of a boysenberry (Rubus loganbaccus × baileyanus Britt.) extract by LC–ESI-MS/MS, MALDI-TOF-MS and NMR spectroscopy

Four ellagitannins from boysenberry, a cross between Rubus loganbaccus and Rubus baileyanus Britt., were isolated by preparative HPLC and the exact structures determined by a combination of LC–ESI-MS/MS, MALDI-TOF-MS and NMR spectroscopy. The two most abundant ellagitannins were identified as sanguiin H-6, which is known to be abundant in Rubus species, and the other was identified as an isomer of sanguiin H-10, which has not previously been reported in Rubus. The two less abundant ellagitannins were identified as sanguiin H-2 and [galloyl–bis-HHDP–glucose]2-gallate. Sanguiin H-2 has been previously reported in Rubus, whereas both sanguiin H-2 and [galloyl–bis-HHDP–glucose]2-gallate have been previously reported as hot-water degradation products of lambertianin C. Even though lambertianin C is reported to be a major ellagitannin in other Rubus species, it was not found in any of the fractions, suggesting that both sanguiin H-2 and [galloyl–bis-HHDP–glucose]2-gallate are present naturally in boysenberry.