Effects of onion and garlic extracts on spontaneously hypertensive rats

Investigation of antihypertensive mechanism of garlic in 2K1C hypertensive rat

This study sought to examine the antihypertensive mechanism of garlic in two-kidney-one-clip (2K1C) hypertensive rat. In this study, the effect of garlic on serum and tissue including: aorta, heart, kidney, lung as well as circulatory (serum) ACE activity in 2K1C rats were examined. Four groups of rats were selected: control "CTL", sham-operated "SHAM", hypertensive "H" and garlic-treated hypertensive "GT" group. Hypertension was induced by surgery. Four weeks post-clipping, single daily dose of 50mg of aqueous extract of garlic was given orally to "GT" rats for 4 weeks. Blood pressure was measured by tail-cuff method. ACE activity was determined using HPLC. The systolic blood pressure (SBP) was significantly increased in "H" compared to "CTL" group. In "GT" group, blood pressure was significantly decreased compared to "H" group. The ACE activity in all tissues of "H" group was significantly increased compared to controls which was significantly decreased in garlic-treated compared to non-treated hypertensive rats. These results indicated a negative correlation between consumption of garlic, blood pressure and ACE activity in serum and different tissues in 2K1C rats, suggesting that garlic has a significant blood pressure lowering effect, which could partly be mediated by reduction in ACE activity.

Garlic and onions: their effect on eicosanoid metabolism and its clinical relevance

Garlic (Allium sativum) and onion (Allium cepa) are among the oldest of all cultivated plants. Additionally, both plants have been used as medicinal agents for thousands of years. Both garlic and onion have been shown to have applications as antimicrobial, antithrombotic, antitumor, hypolipidaemic, antiarthritic and hypoglycemic agents. In recent years, extensive research has focussed on the beneficial and medicinal properties of garlic and onions. In particular, the use of these agents in the treatment and prevention of cardiovascular disease and cancer is an area of considerable investigation and interest.

The antihypertensive effect of garlic (Allium sativum) in the rat two-kidney--one-clip Goldblatt model

A study was designed to elucidate the antihypertensive effect of garlic in the two-kidney--one-clip (2K-1C) Goldblatt model. Since the hypertension in this model depends largely on the increasing concentrations of vasopressor agents (prostaglandins and angiotensin II) there is a strong indication that reducing these factors could contribute in controlling the pathological rise in blood pressure. In this study, single or multiple doses of 0.5 ml of aqueous extract of garlic were given orally to 2K-1C rats. The data shows that the single dose of garlic used had a maximum antihypertensive effect 2-6 h after administration. The residual effect of this single dose continued for up to 24 h. The multiple dose of garlic appeared to be effective in restraining the expected rise in blood pressure that normally occurs in 2K-1C rats. Switching multiple-dose treatments halfway through the experiment further strengthened the findings. The study suggests that garlic does have an effective antihypertensive ability, and may be used as a supplementary and natural remedy in cases of unilateral renovascular hypertension.

Antithrombotic activity of garlic: its inhibition of the synthesis of thromboxane-B2 during infusion of arachidonic acid and collagen in rabbits

Rabbits were given collagen and arachidonic acid intravenously. Blood pressure, platelet counts, plasma thromboxane-B2 (TXB2) and plasma 6-keto-prostaglandin F1 alpha, (6-keto-PGF1 alpha) were determined. Both thrombogenic agents, upon infusion of a lethal dose, caused thrombocytopenia, indicative of in vivo platelet aggregation and hypotension. These changes were associated with an increase in plasma levels of TXB2 and 6-keto-PGF1 alpha measured by radioimmunoassay (RIA). Pretreatment of rabbits with an aqueous extract of garlic (500 mgkg) provided protection from thrombocytopenia and hypotension. Thromboxane-B2 synthesis was significantly reduced in animals pretreated with garlic and then injected with a lethal dose of either collagen or arachidonic acid. The amount of TXB2 synthesized in these animals was not sufficient to induce thrombocytopenia or hypotension. All animals pretreated with garlic were well protected against the effects of collagen or arachidonate infusion, and no apparent symptoms were observed in these animals. These observations indicate that garlic may be beneficial in the prevention of thrombosis.