Angiotensin-converting-enzyme inhibitory activity of Cogon grass (Imperata cylindrica (l.) Beauv.) root ethanolic extract

Abstract

Cogon grass (Imperata cylindrica) root is one of the herbal medicines used as an anti-hypertensive remedy in the Philippines. This study tests its anti-hypertensive activity through the angiotensin-converting-enzyme mechanism. The I. cylindrica roots were collected from three geographical sources: Bacoor, Cavite; Quiapo, & San Mateo, Rizal. These were initially screened using UPLC-MS to determine which among the three showed the greatest inhibitory activity by measuring its capability to hydrolyze Hippuryl-Histidyl-Leucine (HHL) from the excised lungs of mice. The extract from Bacoor, Cavite showed the greatest inhibitory activity, as it exhibited the highest remaining HHL (5.97 x 105 intensity counts) and was used for the in vivo setup. The in vivo setup measures the ACE inhibitory activity by means of its capability to maintain or lower the blood pressure of the mice. Blood pressure measurement was recorded using the tail-cuff method via the MRBP Blood Pressure System Model 31. Subcutaneous injection of Angiotensin I was performed to induce hypertension to the mice. A methanolic extract (200 mg/kg-bw , and three increasing dosages of ethanolic extract (100, 200, 300 mg/kg-bw) were used to assess which among the three concentrations will exhibit the greatest ACE-inhibitory activity. Both setups used a reference drug, captopril, as the positive control since it is a known ACE-inhibitor. The ethanolic extract (300 mg/kg-bw) exhibited the highest decrease in the systolic and diastolic blood pressures (-3.19 mmHg; -0.67 mmHg). UPLC-MS analysis was further conducted to determine which chemical constituent may have caused this decrease in blood pressure. Among the three chemical constituents found (Glutinone, Graminone A, & Cylindrene), Cylindrene was said to be the putative metabolite responsible for the anti-hypertensive activity as mentioned by previous studies.