Study of the ACE Inhibitory Effect of Medicinal Plants Used in Iranian Folk-Medicine as Antihypertensive Remedy

Background: Angiotensin converting enzyme (ACE) is an exopeptidase which converts angiotensin I to angiotensin II. Angiotensin II causes vasoconstriction and aldosteron secretion and inactivate bradykinin, so ACE has major role on blood pressure regulation. Objective In this study 135 plants used in Persian traditional medicine have been investigated for their angiotensin converting enzyme (ACE) inhibitory activity potential. They were selected on the basis of their usage as antihypertensive, cardiotonics & diuretics. Methods: The dried powdered plant material, 1 g was extracted with 10 ml water and ethanol (%96) 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 more then 50% were further tested for the presence of tannins in order to eliminate possible false positives. Results: In total, 52 species out of the 135 (39%) screened, gave more than 50% ACE inhibition. 40 species were found to possess a high ACE inhibiting ability and were low in their tannin content.