Nitric oxide is known as relaxing factor because it acts as a vasodilator, increases blood flow, and inhibits platelet aggregation and adhesion, on the other hand nitric oxide can modulate cellular and physiological processes to limit oxidative injury, limiting processes such as leukocyte adhesion. As the complete mechanism of myricetin and its cardiovascular benefits is not completely understood, the aim of this study was to investigate the antihypertensive activity of myricetin in human umbilical vein endothelial cell (HUVEC). Angiotensin converting enzyme (ACE) activity, nitric oxide production, reactive oxygen species (ROS) scavenger activity, cellular calcium concentration, and endothelial nitric oxide synthase (eNOS) activity and protein expression was investigated in HUVEC treated with different concentration of myricetin (1-60 mu M). Myricetin increased nitric oxide production in HUVEC through decreased ROS levels and increased nitric oxide production and eNOS activation. Activation of eNOS enzyme was achieved by an increase of cellular calcium concentration. At the same examined concentration of myricetin, the activity of ACE was significantly inhibited. These findings indicate that myricetin may be helpful for lowering blood pressure; this could be achieved through dietary intervention or by the production of new antihypertensive treatments from a natural product.