COMPARATIVE EFFECTS OF HORSERADISH (Moringa oleifera) LEAVES AND SEEDS ON KEY ENZYMES LINKED WITH HYPERTENSION

Abstract

This study sought to investigate the effects of moringa leaves on some critical enzymes [angiotensin-1 converting enzyme (ACE), acetylcholinesterase (AChE), arginase, monoamine oxidase (MAO), phosphodiesterase-5 (PDE-5)] relevant to hypertension and antioxidant status in vitro and in vivo. The antioxidant properties of the extracts were evaluated through (ABTS*, DPPH* and OH*) radical scavenging, metal chelating (Fe 2+ ) and inhibition of Fe 2+ and sodium nitroprusside (SNP) induced lipid peroxidation heart in vitro. The results revealed that the extracts of the leaves and seeds both inhibited arginase (IC 50 leaves = 0.77mg/ml; seeds = 1.29mg/ml), AChE (IC 50 leaves = 1.40mg/ml; seeds = 5.41mg/ml) and monoamine oxidase (IC 50 leaves = 0.65mg/ml; seeds = 0.90mg/ml) activity in concentration dependent manner. However, the leaves exhibited a higher inhibitory effect than the seeds. Furthermore, the extract of the leaves had a higher radical scavenging ability, [DPPH* (IC 50 leaves = 0.40mg/ml; seeds = 0.88mg/ml), OH*(IC 50 leaves = 0.31mg/ml; seeds = 0.51mg/ml), Fe 2+ chelating ability (IC 50 leaves = 0.46mg/ml; seeds = 0.93mg/ml) than the seed. The extract of the plant parts also inhibited SNP and Fe 2+ induced lipid peroxidation in heart, in vitro. Hypertensive rats (HYP) were placed on a dietary regimen containing 2% and 4% moringa leaves and seeds. The result revealed that there was a significant increase (p < 0.05) in the average weight changes of HYP in comparison to the normal rat group. Also, there was a significant reduction (p < 0.05) in the blood pressure measurement (systolic and diastolic) in the HYP treated groups compared to the HYP. However, there was no significant difference (p > 0.05) in the blood pressure measurements of the normal control group and the normal groups that were fed 2% and 4% moringa leaves and seeds supplemented diet. In addition, there were significant reductions (p < 0.05) in the activities of arginase, AChE, PDE-5 and ACE of HYP rats treated with 2% and 4% moringa seed and leaves supplemented diet when compared to the HYP group. Also, treatment with 2% and 4% moringa seed and leaves significantly (p < 0.05) elevated the levels of antioxidant status (superoxide dismutase, glutathione-s-transferase, reduced glutathione and catalase) in HYP rats fed diet supplemented with 2% and 4% moringa seed and leaves compared to the HYP. Thus, the antioxidant effects and inhibition of the key enzymes of the leaves and seeds could be part of the possible biochemical mechanisms behind their folkloric use as antihypertensive plants. However, moringa leaves showed higher antihypertensive effects than the seeds.