Antioxidant activity of galloyl quinic derivatives isolated from P. lentiscus leaves.

The antioxidant properties of galloyl quinic derivatives isolated from Pistacia lentiscus L. leaves have been investigated by means of Electron Paramagnetic Resonance spectroscopy (EPR) and UV-Vis spectrophotometry. Antioxidant properties have been also estimated using the biologically relevant LDL test. The scavenger activities of gallic acid, 5-O-galloyl, 3,5-O-digalloyl, 3,4,5-O-trigalloyl quinic acid derivatives, have been estimated against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide (O2) radical, and hydroxyl (OH) radical. On the whole, the scavenger activity raised as the number of galloyl groups on the quinic acid skeleton increased. The half-inhibition concentrations (IC50) of di- and tri-galloyl derivatives did not exceed 30 microM for all the tested free radicals. All the tested metabolites strongly reduced the oxidation of low-density lipoproteins (LDL), following a trend similar to that observed for the scavenger ability against OH radical.