Antihypertensive effects of Brazilian propolis: identification of caffeoylquinic acids as constituents involved in the hypotension in spontaneously hypertensive rats.

Brazilian propolis was extracted with water or various concentrations of ethanol and were administered orally to spontaneously hypertensive rats (SHR) and the effects on blood pressure and heart rate were determined. Single oral administration of 100 mg/kg of propolis extracts decreased the blood pressure in SHR. Significant decrease in blood pressure was observed with propolis extracted with 25 and 70% ethanol. SHR were given orally 5 mg/kg of propolis extracted with 25 or 70% ethanol, twice a day for 28 d and the effects on blood pressure and heart rate were compared with control rats. While the blood pressure in the control group increased day by day, the increase was slower in rats treated with 25 and 70% ethanol extracts of propolis. The hypotensive activity of propolis extracted with 25% ethanol was more significant compared with control group than with 70% ethanol. Di- and tri-caffeoylquinic acids (CQAs) were found to be characteristic components of propolis extracted with 25% ethanol. A single oral administration of 3,4-diCQA, 3,5-diCQA, and 3,4,5-triCQA each at a dose of 10 mg/kg were conducted in SHR. These three components were found to have antihypertensive effects and therefore contribute to the antihypertensive effects of propolis extract. These results suggest that 25% ethanol extract of propolis is useful for prevention and treatment of hypertension.