Results from a small study indicate that supplementation with quercetin may lower blood pressure in hypertensive patients. While the supplement had no effect on those with pre-hypertension, taking 730 mg of quercetin per day was associated with significant reductions in systolic, diastolic and mean arterial pressures in those with stage 1 hypertension.
Source: J Nutr, 2007; 137(11): 2405-11