Characterization of tannins from two wild blackberries (Rubusspp) by LC–ESI–MS/MS, NMR and antioxidant capacity

Tannins are phenolics found in fruits such as wild Rubusberries. The aim of this study was to determine the profile by LC–ESI–MS/MS and NMR, antioxidant capacity (AOX) of the tannins in two Mexican wild blackberries. Fractions rich in tannins (FRT) were isolated using different solvents and chromatographic resins. The LC–ESI–MS/MS and NMR results showed that catechin and epicatechin (m/z289−1), which are precursors of proanthocyanidins, as well as other six oligomeric forms of ellagitannins (m/z301−1) were found in R. Liebmannii, whereas in R. Palmeri, only ellagitannins were found, highlighting oligomeric forms of lambertianins and sanguiins (m/z783−1to 1869−1). The purification pathway made it possible to increase the AOX 19.7 times from fruits to FRT showing strong positive correlations (R2> 0.9) with total phenolic content. This study provided a good assessment of the tannin composition of wild blackberries from the Northwest of Mexico and their bioactivity as a potential edible source.