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 Electronic 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 di-O-galloyl, 3,4,5 tri-O-galloyl quinic acid derivatives, have been estimated against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide (O2-) radical, and hydroxyl (OH) radical. On the whole scavenger activity raised as the number of galloyl groups on the quinic acid skeleton increased. The half-inhibition concentration (IC50) of di- and tri-galloyl derivatives did not exceed 30 micromolar for all the tested free radiacls. 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.