The present invention relates to a composition for treatment and prevention of cardiovascular diseases, containing an extract of Lysimachia clethroides. More particularly, the extract of Lysimachia clethroides strongly inhibits NAD(P)H oxidases, which are the main cause of vascular diseases, and at the same time, regulates contraction and relaxation of vascular smooth muscles to manifest a potent vasorelaxant effect, thereby improving the blood pressure regulation and vascular endothelial dysfunction. Therefore, a composition containing this as an active ingredient can be usefully utilized as a pharmaceutical prodvct or health functional food prodvct for the prevention and treatment of cardiovascular diseases.
