Investigation of Angiotensin-Convertings Enzyme Inhibitory Effects of Medicinal Plants Used in Traditional Persian Medicine for Treatment of Hypertension: Screening Study

Angiotensin converting enzyme (ACE) inhibitors are used widely in the treatment of hypertension and heart failure. These inhibitors such as captopril and enalapril are derived from natural products. In the present study 135 plants used in Traditional Persian Medicine have been investigated for their angiotensin converting enzyme (ACE) inhibitory activity. They were selected on the basis of their usage as antihypertensive, cardiotonics & diuretics. Dried powdered plant material was extracted with mix solution of water and ethanol in ultrasonic bath. The extracts were filtered and concentrated in vacuum except for the water extracts, which were freeze-dried. Test solutions were made by dissolving extract in assay buffer, corresponding to a final concentration of 0.33 mg of crude plant extract in 1 ml test volume. Enzyme assay was performed by HPLC method. Plants exhibiting inhibition levels with more than 50% were further tested for the presence of tannins in order to eliminate possible false positives. In total, 52 Species out of the 135 (39%) screened, gave more than 50% ACE inhibition. Forty Species were found to possess a high ACE inhibiting ability and were low in their tannin content. Traditional medicine based on certain plants could be of beneficial effects in hypertension treatment.