IN VITRO EFFECT OF NARINGIN AND QUERCETIN ON LDL OXIDATION VIA THEIR INFLUENCE IN COPPER BINDING TO LDL

The oxidative modification of low density lipoprotein (LDL) may play an important role in atherogenesis. Mechanism of LDL oxidation and factors that determine its susceptibility to oxidation is unknown. Copper is account as an attributing factor in LDL oxidation atherosclerotic lesions. The binding of copper ions to LDL is usually thought to be a prerequisite for LDL oxidation by copper. The aim of study was to investigate the effect of Naringin and Quercetin on copper bound to LDL and furthermore effect of this binding on the susceptibility of LDL to oxidative modification. LDL was isolated from EDTA-plasma by ultracentrifugation using a discontinuous gradient. The oxidizability of LDL was measured by thiobarbitoric acid reactive substances (TBARS) after addition of CuSO4 in absence and/or presence of Naringin and Quercetin. Finally effect of Naringin and Quercetin on formation of LDL-copper complex was studied by gel filtration. This study showed that Naringin suppresses formation of TBARS and LDL-copper complex, whereas Quercetin enhances formation of TBARS and LDL-copper complex. Results revealed that Naringin with inhibition of binding of Copper to LDL may decrease the susceptibility of LDL oxidation in counter to this ion and thus may have a role in prevention of atherosclerosis. But Quercetin with stimulation of binding of copper to LDL may increase the susceptibility of LDL oxidation to this ion and thus may have a role in progression atherosclerosis.