INHIBITORY ACTIVITIES OF OCIMUM SANCTUM AND ITS FLAVONOID CONSTITUENTS ON ANGIOTENSINCONVERTING ENZYME

As part of our ongoing isolation of antihypertensive agents derived from natural sources, the bioactivity of the ethanolic extracts was screened for their inhibitory activities against angiotensin converting enzyme (ACE) inhibitory assays. Ocimum sanctum exhibited promising inhibitory activity against ACE and Total ROS. Among the different solvent-soluble fractions obtained from the ethanolic extract, the dichloromethane (CH2Cl2) fraction was found to cause the most potent scavenging, or inhibitory activities, against total ROS with the respective IC50 values of 3.21 ± 0.03 µg/mL. Likewise, the dichloromethane fraction also exhibited potent inhibitory activities against ACE with IC50 values of 16.19 ± 0.12 µg/mL. Silica gel column chromatography of the dichloromethane fraction yielded two flavonoids, Cirsilineol and Isothymusin, based on the comparison with reported 1H- and 13C-NMR spectroscopic data. All of the compounds displayed concentration dependent in vitro inhibitory activity toward the ACE and Total ROS. Among them, Cirsilineol exhibited the potential inhibitory activity toward ACE with the respective IC50 values of 12.64 ± 0.02 µM. Further inhibitory kinetics analyzed from Lineweaver-Burk plots showed Cirsilineol to be a competitive inhibitor with a Ki value of 8.2 × 10−5 M. In conclusion, we identified significant ACE inhibitors from Ocimum sanctum that could have value as new multitargeted compounds for antihypertensive agents. Keywords: O. sanctum; Hypertension; Antioxidant; Angiotensin Converting Enzyme (ACE); Total Reactive Oxygen Species (ROS).