Mass Spectrometry and 1H-NMR Study of Schinopsis lorentzii (Quebracho) Tannins as a Source of Hypoglycemic and Antioxidant Principles

摘要

The ethyl acetate extract of the commercial tannin Tan’Activ QS-SOL (from wood), employed for the production of red wine, was subjected to chromatography on Sephadex LH-20, providing nine fractions (A-1–A-9), which were estimated for total phenols content (GAE), antioxidant activity (DPPH, ORAC), and hypoglycemic activity (α-glucosidase and α-amylase inhibition). All the fractions were analyzed by means of HPLC/ESI-MS/MS and H-NMR to identify the principal active constituents. Fractions A-1 and A-3 showed the highest antioxidant activity and gallic acid ( ), pyrogallol ( ), eriodictyol ( ), catechin ( ), and taxifolin ( ) were identified as the major constituents. The highest α-glucosidase and α-amylase inhibitory activity was observed in fractions A-7–A-9 containing condensed ( , , , , , and ) hydrolysable tannins ( and ) as well as esters of quinic acid with different units of gallic acid ( , , , , and ). This last class of gallic acid esters are here reported for the first time as α-glucosidase and α-amylase inhibitors.