Moringa oleifera leaves methanolic extract inhibits angiotensin converting enzyme activity in vitro which ameliorates hypertension

Angiotensin Converting Enzyme (ACE) regulates blood pressure. ACE converts angiotensin I to angiotensin II which binds with its receptors and through a cascade of reactions constrict blood vesels, consequently results in increased blood pressure, called hypertension. Inhibition of ACE activity is considered as an useful therapeutic target that reduce hypertension. Moringa oleifera leaves have traditionally been used in Ayurvedic medicine for their antihypertensive activity and antihypertensive effect of Moringa leaves was reported on spontaneously hypertensive rats. So, we hypothesize that Moringa oleifera leaves methanolic extract (MOLME) might inhibit ACE activity. Inhibition of ACE activity by MOLME was estimated in vitro. In this study, inhibition of ACE by MOLME was evaluated by spectrophotometric method. MOLME inhibited ACE activity in the substrate hippuryl-L-histidyl-L-leucine (HHL) with an IC50 value of 226.37 μg/ml with a reference compound, captropril (CP), a potent ACE inhibitor with an IC50 value of 0.0289 μM. The mode of ACE inhibition in HHL with or without MOLME revealed that the Vmax (0.0857 and 0.0541 OD/30 min, respectively) was changed and the Km values were 4.671 and 4.41. The results indicate that MOLME acts as a non-competitive inhibitor for ACE. CP was found a competitive inhibitor of ACE. MOLME might be a potential natural inhibitor of ACE which reduces hypertension.