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Investigation of the Antihypertensive Effect of Oral Crude Stevioside in Patients with Mild Essential Hypertension

Stevia rebaudiana (Bertoni) Bertoni (Compositae) is a perennial native shrub from north-eastern Paraguay and southern Brazil (Geuns, 2002).The leaves of Stevia rebaudiana (Bertoni) Bertoni have been used by Guarani Indians from Paraguay to treat diabetes and this empirical knowledge was passed by oral tradition for many centuries (Bazotte et al.,1986). This empirical knowledge led to several investigations on the antidiabetic properties of this plant including previous studies which confirmed that treatment with Stevia rebaudiana (Bertoni) Bertoni leaves could reduce fasting glycaemia in rats (Ueda et al., 1983)and in humans (Curi et al., 1986).In Brazil, the reports on Stevia rebaudiana (Bertoni) Bertoni started with Boech, who first demonstrated the hypotensive effect of crude stevioside in rats (Humboldand Boech, 1978). Since this study, several publications confirmed the antihypertensive properties of crude stevioside in rats (Melis, 1992a,b,c; Chan et al., 1998;Melis, 1999; Lee et al., 2001; Hsu et al., 2002) and in dogs (Liu et al., 2003). The antihypertensive effect of stevioside was attributed to an inhibition of extracellular calcium influx (Melis, 1992a; Lee et al., 2001).Furthermore, two clinical trials investigated the effect of crude stevioside on systolic (SBP) and diastolic(DBP) blood pressure (Chan et al., 2000; Hsieh et al.,2003). In both reports, the toxicological profile was restricted to hematology and serum evaluation of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine phosphokinase (CPK) and electrolytes.In the present investigation the antihypertensive potential of oral crude stevioside obtained from the leaves of Stevia rebaudiana (Bertoni) Bertoni cultivated in northeastern Paraguay and southern Brazil was evaluated in a prospective, randomized, double-blind, placebo-controlled, single-center clinical trial. Moreover, the toxicological profile was expanded by assessing metabolic and hormonal parameters that were not evaluated by those studies (Chan et al., 2000; Hsiehet al., 2003)