Quantitative Analysis of Vasodilatory Action of Quercetin on Intramural Coronary Resistance Arteries of the Rat In Vitro

Background: Dietary quercetin improves cardiovascular health, relaxes some vascular smooth muscle and has been demonstrated to serve as a substrate for the cyclooxygenase enzyme. Aims: 1. To test quantitatively a potential direct vasodilatory effect on intramural coronary resistance artery segments, in different concentrations. 2. To scale vasorelaxation at different intraluminal pressure loads on such vessels of different size. 3. To test the potential role of prostanoids in vasodilatation induced by quercetin. Methods: Coronary arterioles (70-240 mu m) were prepared from 24 rats and pressurized in PSS, using a pressure microangiometer. Results: The spontaneous tone that developed at 50 mmHg was relaxed by quercetin in the 10(-9) moles/lit concentration (p<0.05), while 10(-5) moles/lit caused full relaxation. Significant relaxation was observed at all pressure levels (10-100 mmHg) at 10(-7) moles/lit concentration of quercetin. The cyclooxygenase blocker indomethacin (10(-5) moles/lit) induced no relaxation but contraction when physiological concentrations of quercetin were present in the tissue bath (p<0.02 with Anova), this contraction being more prominent in smaller vessels and in the higher pressure range (p<0.05, Pearson correlation). A further 2-8% contraction could be elicited by the NO blocker L-NAME (10(-4) moles/lit). Conclusion: These results demonstrate that circulating levels of quercetin (10(-7) moles/lit) exhibit a substantial coronary vasodilatory effect. The extent of it is commeasurable with that of several other physiological mechanisms of coronary blood flow control. At least part of this relaxation is the result of an altered balance toward the production of endogenous vasodilatory prostanoids in the coronary arteriole wall

The Efficacy of Quercetin in Cardiovascular Health

Cardiovascular disease is a major cause of death worldwide despite the majority of its risk factors being preventable and treatable. The results of numerous epidemiological studies suggest that a diet rich in fruits and vegetables affords protection against CVD, and this may be attributed, in part, to the flavonoid quercetin. The aims of this review are to summarise the current knowledge on the bioavailability and metabolism of quercetin as well as discuss the current evidence behind the potential mechanisms by which quercetin exerts its cardioprotective effects. This review summarises key human studies administering quercetin that have been published to date. Although interesting results have been seen in animal and cell culture studies, in general, these have not been replicated in human trials. Several studies have, however, shown that quercetin can reduce blood pressure in hypertensive patients. The exact mechanisms are yet to be elucidated. Further studies are required to investigate the use of quercetin as a cardioprotective treatment, in particular long-term and dose–response studies