ON THE IMPORTANCE OF USING DIFFERENT RADICAL SOURCES TO INVESTIGATE THE SCAVENGING PROPERTIES OF GRAPE TISSUES AND WINES

In an attempt to shed light on the specific free radical scavenging capacities of grape tissues towards specific ROS, an electron paramagnetic resonance (EPR) study was conducted on grape and wine extracts, from two cultivars of Vitis vinifera L., to evaluatetheir antiradical capacity (AC) against  and ·OH. Furthermore, we also evaluated the  overall AC of analyzed samples by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH·)spectrophotometric assay, comparing the obtained results from the antiradical methods used in order to find a suitable procedure for the investigation of the antiradical properties of the metabolites localized in different parts of the grape berry and in the wine. The difference in AC among the various grape tissues decreased a great deal if the AC was measured withthe EPR test for OH·. In fact, while the DPPH· and scavenging capacity were significantly correlated  the antiradical test for OH· did not correlate with any of the two methods. Moreover, superoxide anion scavenging capacity showed a high correlation with flavans  and only to a lesser extent with polyphenols  The hydroxyl radical scavenging capacity showed low correlations with analyzed phytochemicals, giving the chance to assume a role of other substances in the scavenging of this harmful oxygen radical (i.e., sugars, organic acids). These findings suggest the convenience in taking into account the OH· test when determining the total AC of such a complex matrix like grapes.

Malvasia del Lazio, Cabernet Sauvignon, DPPH·, EPR, grape tissues.