| In vitro: |
| Food Chemistry, 2017, 215:50-60. | | α-Glucosidase inhibition and antioxidant activity of an oenological commercial tannin. Extraction, fractionation and analysis by HPLC/ESI-MS/MS and 1H NMR.[Reference: WebLink] |
METHODS AND RESULTS:
Two batches of the oenological tannin Tan’Activ R, (toasted oak wood – Quercus robur), were extracted with ethanol.
A fractionation on XAD-16 afforded four fractions for each extract. Extracts and fractions were evaluated for antioxidant activity (DPPH), polyphenol content (GAE) and yeast α-glucosidase inhibitory activity.
CONCLUSIONS:
Comparable results were obtained for both columns, fractions X1B and X2B showing the highest antioxidant activity. Fractions X1C and X2C notably inhibited α-glucosidase, with IC50 = 9.89 and 8.05 μg/mL, respectively. Fractions were subjected to HPLC/ESI-MS/MS and 1H NMR analysis. The main phenolic constituents of both X1B and X2B were a monogalloylglucose isomer (1), a HHDP-glucose isomer (2), Castalin (3) gallic acid (4), vescalagin (5), and grandinin (or its isomer roburin E, 6). X1C and X2C showed a complex composition, including non-phenolic constituents. Fractionation of X2C gave a subfraction, with enhanced α-glucosidase inhibitory activity (IC50 = 6.15 μg/mL), with castalagin (7) as the main constituent. |
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