The polyphenolic composition and antioxidant properties of the methanol leaf extract of Vitis × Labruscana cv.
‘Isabella’ has been performed by means of different spectrophotometric antioxidant methods. Intracellular ROS production
was measured by cell fluorescence after loading with 2',7'-H2DCF-DA. The extract promising efficacy has laid the
basis to its phytochemical characterization. Three hydroxycinnamoyl tartaric acids (1-3 ), isoquercitrin 4, and five flavonol
glycuronides (5-9) were isolated from Vitis × Labruscana cv. ‘Isabella’ leaves. Chemical structures were elucidated on the
basis of their spectroscopic features. Metabolites 6, 7, and 9, characterized by glucuronic or galacturonic acid methyl ester,
are described from the genus Vitis for the first time. The metabolites isolated as major constituents were investigated
for their DPPH radical scavenging capacity.