Oxidative modification of low-density lipoprotein (LDL) appears to play a pivotal role in atherosclerosis. In the present study the effect of several concentrations of rutin, its aglycon quercetin, cyanidin 3-O-β-d-glucoside, its aglycon cyanidin, hydroxycinnamic acids, and a standardized red orange (Citrus sinensis varieties) extract (ROE) on LDL oxidation was tested. Lipid peroxidation was monitored by conjugated diene formation and by different electrophoretic mobility of native LDL and oxidized LDL. Results obtained in the present study suggest specific effects of flavonoids tested and, in particular, of ROE on the prevention of LDL oxidation involved in the development of cardiovascular diseases.