Cardiovascular effects of <i>Harpagophytum procumbens</i> dc [Pedaliaceae] secondary root aqueous extract in some mammalian experimental animal models

Abstract

In an attempt to scientifically appraise the ‘healing powers\' and medicinal value of Harpagophytum procumbens DC root aqueous extract (HPE), and throw some light on the efficacy and safety of the medicinal plant product, the cardiovascular effects of the herb\'s root aqueous extract (HPE) have been investigated in some mammalian experimental animal models. The results of this laboratory animal study indicate that relatively low to moderate doses of H. procumbens root aqueous extract (HPE, 10–400 mg/kg i. v.) produced dose-dependent hypotensive and cardio-depressant effects on systemic arterial blood pressures and heart rates of pentobarbitone-anaesthetized rats. Relatively low to high concentrations of the plant\'s extract (HPE, 10–1000 g/ml) also produced concentration-related biphasic responses in isolated cardiac muscle strips of guinea-pigs and isolated portal veins of rats. Relatively low concentrations of the plant\'s extract (HPE, 10–100 g/ml) always produced initial slight, transient and non-significant (P 0.05) positive chronotropic responses in isolated spontaneouslybeating right atria, but significant (P 0.05) positive inotropic responses in isolated electricallydriven left atria of guinea-pigs. However, moderate to high concentrations of the plant\'s extract (HPE, 400–1000 g/ml) always induced dose-dependent, significant (P 0.05–0.001), secondary longer-lasting, negative chronotropic and inotropic responses of the isolated spontaneouslybeating right-, and isolated electrically-driven left-, atrial muscle preparations of guinea-pigs. The plant\'s extract also produced concentration-related biphasic effects on rat isolated portal vein. Low to high concentrations of the plant\'s extract (HPE, 10–1000 g/ml) always produced dose-dependent, initial slight, transient and significant (P 0.05–0.001) contractions of the rat isolated portal veins, followed by secondary, longer-lasting, significant (P 0.05–0.001) relaxations of the muscle preparations. Although the precise mechanisms of the hypotensive and cardio-depressant actions of HPE are unknown, the vasorelaxant action of the plant\'s extract is speculated to contribute, at least in part, to the hypotensive action of the plant\'s extract. The results of this laboratory animal study lend pharmacological credence to the suggested folkloric uses of Harpagophytum procumbens secondary root in the management and/or control of hypertension and certain cardiac disorders in some communities of South Africa.


Key Words: Harpagophytum procumbens, cardiovascular effects.


Afr. J. Trad. CAM (2004) 1: 30-44