Investigation of the effects of extracts of Manilkara zapota (L.) P. van Royen on blood pressure and heart rate of rats

RESUMO

The objective of the study was to investigate the hypotensive effect produced by leaf extracts of Manilkara zapota. Methanol extracts of Manilkara zapota leaves were prepared using a soxhlet apparatus. The methanol was removed with a rotor evaporator. Sprague-Dawley rats were anaesthetized with urethane (1.2 mg/kb) and doses of 0.63, 1.25, 2.5, 5.0, 10.0 and 20.0 mg/kg body weight of extract were administered intavenously. Saline (0.9 percent) was given as a control. The effects on blood pressure and heart rate were recorded using a Pressure transducer (Spectramed model 23XL) coupled to a Grass polygraph (model 79E). The plant extract showed a dose-related hypotensive activity and no significant change in heart rate (P.0.05). Toxicity was observed with doses greater than 20mg/kg body weight. These results indicate that Manilkara zapota leaf tea used in folklore medicine to treat hypertension does indeed show various degrees of hypotensive activity when tested in lab animals. However, larger doses were toxic. It is therefore necessary to assess the beneficial as well as the adverse effects of this herb before usage by the hypertensive patient