Biol. Pharm. Bull. 28(10) 1909—1914 (2005)

tension, arteriosclerosis, heart disease, obesity, diabetes mellitus, and cancers have become a great social problem. As regards diseases of circulatory system such as hypertension, arteriosclerosis and heart disease, increasing numbers of people are showing symptoms of hypertension or pre-hypertension stage. Causes leading to hypertension include increase in the volume of body fluid, increase of the resistivity of the blood vessels, increases in factors leading to elevation of the blood pressure or decreases in factors bringing about lowering of the blood pressure. These factors induce abnormal increase of blood pressure, either singly or in combination. Clinically, various drugs such as inhibitors of angiotensin converting enzymes, calcium antagonists, b-blockers, angiotensin II receptor antagonists, and hypotensive diuretics have been used for management of hypertension to improve the symptoms. In addition, antihypertensive effects have been noted with various food and natural products. Recently, various foods with differing hypotensive mechanisms have been specified for use as health foods. These foods have various activities such as the inhibitory activity of peptides derived from milk, fish, or plants, on angiotensin converting enzymes, vasodilatory action by parasympathetic stimulation, or inhibitory effects on release of noradrenaline from sympathetic nerves, respectively. Furthermore, some flavonoids and polyphenol derivatives from natural products have been reported to have vasodilating and hypotensive effects. In these points, we focused on propolis which has been shown to comprise more than 150 constituents, including cinnamic acid derivatives, flavonoids, and benzoic acids. Propolis is called “bee resin”, which is a yellow to dark brown-colored adhesive substance collected from sprouts of plants by honeybees and thought to serve a protective role against potential predators. Propolis has been reported to possess some pharmacological functions in humans such as antibacterial, antioxidative, anti-inflammatory, antitumor, and immunostimulatory activities and has been used in folk medicine. The composition of propolis primarily depends upon the vegetation of the area from where it was collected and secondarily upon the solvents used for its extraction. Although pharmacological activities of propolis could be related to its chemical composition, water or 90—99.5% ethanol extract of propolis is commonly used for health food and beverages in recent years. Since Baccharis dracunculifolia is an important source of propolis collected from Minas Gerais state, Brazil, which is of good quality to provide experimental reproducibility, we have used this Brazilian propolis in the current study. In the course of studies on diverse pharmaceutical activities of propolis, we examined hypotensive effects of Brazilian propolis extracts. Recent study reported that caffeic acid phenethyl ester (CAPE), which is one of the major components of propolis from Europe and Asia but not be contained in that from Brazil, has vasodilating activity on isolated rat aorta. Furthermore, the hypotensive effect of propolis extract in spontaneously hypertensive rats (SHR) was reported. However, information concerning effective extraction and ingredients underlying the hypotensive effect of Brazilian propolis have not been available. In this study, at an initial effort insight into hypotensive effects of Brazilian propolis, effects of various propolis extracts on blood pressure and heart rate were examined using SHR. Furthermore, the potency of caffeoylquinic acid derivatives from propolis to induce hypotensive effects were elucidated.