Activity of myricetin and other plant-derived polyhydroxyl compounds in human LDL and human vascular endothelial cells against oxidative stress

Studies indicate that oxidative modifications of endothelium and LDL play a preeminent role in atherogenesis; therefore, the preservation of the endothelial antioxidant capacity and the inhibition of LDL oxidation by use of plant-derived compounds are an appealing strategy against several vascular disorders. On this basis, baicalein, eupatorin, galangin, magnolol, myricetin, oleuropein, silibinin and bilobalide were studied against various oxidative conditions. The radical scavenging capacity was analysed using DPPH and ORAC assays. Furthermore, the LDL oxidation was detected by measuring the formation of thiobarbituric acid reactive substances (TBARS) and by monitoring the oxidation kinetics. Further, we used cultured HUVEC to investigate the activities of the polyhydroxyl compounds towards the oxidative stress induced by H2O2. The lowest levels of TBARS were observed in the presence of oleuropein and baicalein, while myricetin, magnolol and eupatorin inhibited these ones to a lesser extent. In addition, oleuropein and myricetin exhibited higher protection in copper-induced LDL oxidation kinetics. However, only myricetin and galangin showed significant protective effects against H2O2 oxidative injury in HUVEC cells. Taken all together the results indicate myricetin as the most active agent among the selected plant-derived polyhydroxyl compounds, with prominent capacities against ox-LDL and ROS production in HUVEC.