title: Discovery of new angiotensin converting enzyme (ACE) inhibitors from medicinal plants to treat hypertension using an in vitro assay.
abstract: OBJECTIVE
  Angiotensin converting enzyme (ACE) inhibitors plays a critical role in treating hypertension. The purpose of the present investigation was to evaluate ACE inhibition activity of 50 Iranian medicinal plants using an in vitro assay.
  
  
  METHODS
  The ACE activity was evaluated by determining the hydrolysis rate of substrate, hippuryl-L-histidyl-L-leucine (HHL), using reverse phase high performance liquid chromatography (RP-HPLC). Total phenolic content and antioxidant activity were determined by Folin-Ciocalteu colorimetric method and DPPH radical scavenging assay respectively.
  
  
  RESULTS
  Six extracts revealed > 50% ACE inhibition activity at 330 μg/ml concentration. They were Berberis integerrima Bunge. (Berberidaceae) (88.2 ± 1.7%), Crataegus microphylla C. Koch (Rosaceae) (80.9 ± 1.3%), Nymphaea alba L. (Nymphaeaceae) (66.3 ± 1.2%), Onopordon acanthium L. (Asteraceae) (80.2 ± 2.0%), Quercus infectoria G. Olivier. (Fagaceae) (93.9 ± 2.5%) and Rubus sp. (Rosaceae) (51.3 ± 1.0%). Q. infectoria possessed the highest total phenolic content with 7410 ± 101 mg gallic acid/100 g dry plant. Antioxidant activity of Q. infectoria (IC50 value 1.7 ± 0.03 μg/ml) was more than that of BHT (IC50 value of 10.3 ± 0.15 μg/ml) and Trolox (IC50 value of 3.2 ± 0.06 μg/ml) as the positive controls.
  
  
  CONCLUSIONS
  In this study, we introduced six medicinal plants with ACE inhibition activity. Despite the high ACE inhibition and antioxidant activity of Q. infectoria, due to its tannin content (tannins interfere in ACE activity), another plant, O. acanthium, which also had high ACE inhibition and antioxidant activity, but contained no tannin, could be utilized in further studies for isolation of active compounds.
authors.forename: Niusha
authors.initials: N
authors.lastname: Sharifi
authors.forename: Effat
authors.initials: E
authors.lastname: Souri
authors.forename: Seyed Ali
authors.initials: SA
authors.lastname: Ziai
authors.forename: Gholamreza
authors.initials: G
authors.lastname: Amin
authors.affiliation: Department of Medicinal Chemistry, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran. amanlou@tums.ac.ir.
authors.forename: Massoud
authors.initials: M
authors.lastname: Amanlou