Quercetin and alpha-tocopherol prevents the accumulation of lipids and glycoprotein components in myocardial infarcted rats by their anti-lipid peroxidative effect. This was the conclusion of a study at the Annamalai University, India . This study evaluated the combined effects of quercetin and alpha-tocopherol on lipid metabolism and glycoprotein components in isoproterenol induced myocardial infarction in rats. Treatment with the antioxidants significantly reduced the serum levels of cholesterol, triglycerides, free fatty acids and phospholipids. They also significant decreased lipid peroxidation products and increased the enzymatic activity the liver. Pretreatment with quercetin or alpha-tocopherol resulted in a significant improvement of all the biochemical parameters, but a combined treatment normalized all biochemical parameters.
Cardiac hypertrophy, an increase in the size of the heart, can lead to cardiovascular mortality and morbidity. A study lead by Han of the Department of Thoracic and Cardio vascular Surgery, FuTian Hospital, China, found that quercetin appeared to block the development of cardiac hypertrophy induced by pressure overload in rats . Han and coworkers found that quercetin acted by reducing the oxidant status and inhibiting the activities of ERK1/2, p38 MAP kinase, Akt and GSK-3beta. The cardiac hypertrophy induced in rats by an aortic constriction resulted in an increased heart to body weight ratio and malonyldialdehyde level. This increased production of malonyldialdehyde was attenuated by quercetin treatment.
Perez-Vizcaino F and his team at University Complutense of Madrid made a review of the blood pressure lowering effect of quercetin  Studies with rat models of high blood pressure, such as spontaneously hypertensive rats, L-NAME-treated rats and DOCA-salt hypertensive rats showed that quercetin induced a progressive, dose-dependent and sustained reduction in blood pressure. Quercetin also reduced blood pressure in rat models of metabolic syndrome. The phytochemical also prevented changes to the heart, vessels and kidney. The scientists concluded that quercetin could propose reduced the risk of myocardial infarction and stroke. Quercetin may also help to reduce the severity of an hearth attack. Wan and co-workers of the Huazhong University of Science and Technology, China, found that quercetin inhibited the production of NADPH oxidases 2 (NOX2), inducible nitric oxide synthases (iNOS) and endothelial nitric oxide synthases (eNOS) after myocardial ischemia-reperfusion . These enzymes are involved in the pathophysiology of myocardial ischemia-reperfusion injury.
Gong M and colleagues suggested that quercetin has antiatherogenic effect by up regulating paraoxonase 1 gene expression and by preventing LDL oxidation . Paraoxonase 1 is an important anti-atherosclerotic component of high-density lipoprotein and protects the oxidative modification of low-density lipoprotein. They found that quercetin increased the hepatic expression of paraoxonase 1 by 35% and that the lag time of low-density lipoprotein oxidation was increased by more than 3-fold.
A Spanish study conducted by the University of Granade and lead by Sanchez M, analyzed the effect of quercetin and its methylated metabolite isorhamnetin on the endothelial dysfunction of rats after treatment with angiotensin II, which is a potent direct vasoconstrictor, constricting arteries and veins and increasing blood pressure . Both quercetin and isorhamnetin inhibited the adverse effects of angiotensin II. These phytochemicals prevented angiotensin-induced endothelial dysfunction by reducing the increased production of reactive oxygen species, resulting in increased nitric oxide bioavailability.
 Combined effects of quercetin and alpha-tocopherol on lipids and glycoprotein components in isoproterenol induced myocardial infarcted Wistar rats. Chem Biol Interact. 2009 Jul 9.
 Quercetin prevents cardiac hypertrophy induced by pressure overload in rats. J Vet Med Sci. 2009 Jun;71(6):737-43.
 Antihypertensive effects of the flavonoid quercetin. Pharmacol Rep. 2009 Jan-Feb;61(1):67-75.
 Effects of quercetin on gene and protein expression of NOX and NOS after myocardial ischemia and reperfusion in rabbit. Cardiovasc Ther. 2009 Spring;27(1):28-33.
 Quercetin up-regulates paraoxonase 1 gene expression with concomitant protection against LDL oxidation.
Biochem Biophys Res Commun. 2009 Feb 20;379(4):1001-4.
 Quercetin and isorhamnetin prevent endothelial dysfunction, superoxide production, and overexpression of p47phox induced by angiotensin II in rat aorta. Journal of Nutrition. 2007 Apr;137(4):910-5.