Abstract:
Angiotensin-I Converting Enzyme (ACE) inhibitors are the common drugs used in the management of hypertension and they are mostly combined with traditional therapies in Nigeria. However, there is dearth of information on the effect of this combination on the effectiveness of ACE inhibitors. Therefore, this study investigated the effect of aqueous extracts of moringa (Moringa oleifera) leaves on the ACE inhibitory action of lisinopril. The ACE inhibitory activities of various combinations of Moringa extracts and lisinopril (75:25, 50:50, 25:75) were assessed. Furthermore, the ability of the various combinations of moringa and lisinopril to inhibit Fe2+ - induced malondialdehyde (MDA) production in heart and lung homogenates in vitro were assessed, as well as their antioxidant activities as typified by the radicals (DPPH, ABTS) scavenging abilities, Fe2+ chelating abilities and ferric reducing antioxidant. The phenolic content of the moringa leaf extracts were also characterized using HPLC-DAD. The results revealed that moringa had significantly higher ACE inhibitory ability than lisinopril. However, lisinopril had an antagonistic effect on the inhibitory ability of Moringa. Furthermore, lisinopril had stronger Fe2+ chelating while moringa leaf had stronger ABTS radical scavenging ability, stronger DPPH radical scavenging ability and MDA inhibition. However, the antioxidant properties of the various combinations of moringa and lisinopril were significantly lower than those of the individual samples. The HPLC finger-printing of the Moringa leaf extracts revealed the presence of significant amounts of gallic acid (105.67mg/g), chlorogenic acid (79.31mg/g), rutin (60.38mg/g), quercetin (137.81mg/g) and kaempferol (106.75mg/g). Conclusively, the antagonistic effect displayed when ACE inhibition and antioxidant properties displayed when lisinopril and moringa leaf extracts are combined could discourage the use of such combinations in the management of hypertension.
