Solvent fractions and decoction of Eleusine indica leaves were tested for their ability to inhibit angiotensin-converting enzyme (ACE), an important component of the Renin-AngiotensinAldosterone System which is a critical regulator of arterial blood pressure. The ACE inhibitory activity of each fraction was measured by employing a colorimetric assay based on the hydrolysis of histidyl-hippuryl-leucine (HHL) by ACE. Preliminary assay results revealed that the ethyl acetate fraction exhibited the highest antihypertensive activity with a percent inhibition of 51.51%. This fraction was considered for further isolation using a bioassay-guided fractionation scheme. Regulation of blood pressure by RAAS is via angiotensin release and body electrolyte content via aldosterone release. 6 One component of the RAAS is the hydrolase, AngiotensinConverting Enzyme (ACE), is responsible for converting angiotensin I to angiotensin II, a known potent vasoconstrictor. Angiotensin II stimulates both the synthesis and release of aldosterone from the adrenal cortex resulting to an increase in blood pressure via sodium retention.7 Thus, the concept of inhibiting ACE became a popular and effective therapeutic approach in treating hypertension and other cardiovascular diseases. The first oral ACE inhibitor, captopril, l was considered a breakthrough in managing blood pressure and was also an early example of a structure-based drug design. 4 Other synthetic ACE inhibitors which are widely used for clinical use in the treatment of hypertension include enalapril, alcacepril, and lisinopril.8 Just like the early antihypertensive drugs, synthetic ACE inhibitors are also associated with a few side effects such as dry cough and angioedema. The current trend in anti-hypertensive drug research is finding potential ACE inhibitors from natural products that mimic synthetic ACE inhibitors and provide health benefits without adverse effects. There have been several bioactive compounds extracted from plants which were found to possess in vitro ACE inhibitory activity such as flavonoids, hydrolasable tannins, phenylpropanes, xanthones, fatty acids, terpenoids, alkaloids, proanthocyanidins, oligosaccharides, and peptide amino acids. chloride (BSC) to develop the yellow color. Then the absorbance was measured at 410 nm using a microplate reader. The following formula was used to determine percent inhibition: Vacuum liquid chromatographyThe crude fraction with the highest percent inhibition was subjected to vacuum liquid chromatography (VLC). A short column was dry-packed with 70.0 g of silica using suction and manual pressing to make a sorbent bed (bed volume of 150 mL) onto which the sample, preadsorbed in silica, was added. Then the column was pre-treated with 300-mL hexane under light suction. Thereafter, the column was successively eluted with a series of solvents consisting of hexane, hexane combined with increasing amounts of ethyl acetate in 10% increment, ethyl acetate, ethyl acetate combined with methanol (1:1), and methanol. Methanol w...