Testing various herbs for antithrombotic effect

Abstract

Objective

Prevention of arterial thrombotic diseases has high priority in developed countries. Because people who eat inappropriate food are prone to thrombotic events, regular intake of an antithrombotic diet may offer a convenient and effective way of prevention. The aim of the present study was to find herbs that have antithrombotic effects.

Methods

Herbs were crushed and centrifuged and the juice obtained was filtered. The effect of filtrate on platelet-rich thrombus formation was assessed by a shear-induced in vitro platelet function test (hemostatometry). Filtrates showing significant antithrombotic activity were further assessed by using a laser-induced in vivo thrombosis test in mice. The effect of orally administered herb filtrates on flow-mediated vasodilation was also measured.

Results

Common thyme and rosemary showed significant antithrombotic activity in vitro and in vivo. Neither herb affected flow-mediated vasodilation.

Conclusion

Some herbs possess antithrombotic effects in experimental models of thrombosis. The mechanism of the antithrombotic effect of common thyme and rosemary may involve a direct inhibitory effect on platelets.

Introduction

Prevention of “life-style related atherothrombotic diseases” such as myocardial infarction and stroke is an important and urgent social task in many developed countries. Epidemiologic studies have provided irrefutable evidence for the causative role of inappropriate diet in the development and clinical outcome of thrombotic diseases.

Mortality from cardiovascular diseases is significantly lower in French people who otherwise consume a high-fat diet than in people from other countries who consume similar high-fat diets [1]. It was suggested that habitual consumption by the French of large amounts of red wine might be responsible for the decreased cardiovascular mortality rate [2]. This “French paradox” has stimulated experimental studies aimed at finding antithrombotic fruits and vegetables. Epidemiologic studies have provided evidence that foods with experimentally proved antithrombotic effect could prevent coronary events and stroke [3], [4], [5], [6], [7].

Red wine has an antithrombotic effect in various experimental thrombosis models. A special red wine (Chateauneuf-du-Pape 1987) that was brewed from a particular type of grape and a grape juice (Welch’s natural purple grape juice) exerted a significant antithrombotic effect [8]. Extract of a particular variety of raw onion also showed antithrombotic activity [9]. In contrast to grape juice, orange juice purchased from the market and grapefruit juice prepared without special attention to variety had no antithrombotic effect [10]. Wine (red or white) and spirits, but not beer, were found to have preventive effects against stroke [11]. However, another study reported no difference in the preventive effect of beer, white wine, or red wine with respect to cardiovascular mortality and concluded that, in addition to the alcohol, the frequency of drinking was the decisive factor [12]. Without adequate further studies, these contradictions cannot be resolved.

In arterial thrombotic diseases such as cardiovascular disease and stroke, platelets play a pivotal role. Therefore, fruits and vegetables may have antiplatelet effects that need to be tested. The conventional in vitro platelet function test is platelet aggregometry, which measures platelet aggregation in response to various chemical agonists such as adenosine diphosphate, collagen, or epinephrine. Platelet aggregation can also be induced by shear forces and such aggregation is more similar to the pathologic process of arterial thrombosis [13], [14]. Further, an in vitro test performed from native, non-anticoagulated blood has much more relevance to in vivo than those tests performed from anticoagulated blood [15], [16], [17], [18], [19], [20], [21], [22], [23]. By testing native blood samples and using a shear-induced platelet function test (hemostatometry) and a laser-induced thrombosis test in the carotid artery of mice, we previously identified an antithrombotic variety among many tomato varieties [24]. An antithrombotic onion also has been identified with these tests [25].

The aim of the present study was to screen herbs for antithrombotic effect by using a primary in vitro platelet function test and a secondary laser-induced in vivo carotid artery thrombosis test.