Evaluation of In Vitro Angiotensin–Converting  Enzyme Inhibitory Activity of Psidium Guajava  Linn. Leaf Extract and A Study on Enzyme  Kinetics

Jomon Sebastian; Jency Blesson

Volume : I, Issue : VI, November - 2012

Evaluation of In Vitro Angiotensin–Converting Enzyme Inhibitory Activity of Psidium Guajava Linn. Leaf Extract and A Study on Enzyme Kinetics

Jomon Sebastian, Jency Blesson

Abstract :

Psidium guajava Linn. leaf is used traditionally in Indian medicine to control hypertension in human. The aim of this work was to study the hypotensive effect of Psidium guajava leaf extract in human. Hypertension is due to the activity of the Angiotensin–Converting Enzyme that catalyzes the conversion of the inactive Angiotensin I to the active Angiotensin II. Angiotensin II functions as a potent vasoconstrictor causing hypertension. Hence, ACE inhibitors are considered to be the first choice treatment of hypertension. The ACE inhibitory activity of Psidium guajava leaf extract in human was studied by its in vitro inhibitory effect on human serum–huACE using the substrate FA–PGG (N–(3–(2–Furyl) acryloyl)–L–phenylalanyl–glycyl–glycine). The enzyme kinetics of ACE inhibition was investigated by Michaelis–Menten kinetics and Lineweaver–Burk graph and Vmax and Km values were calculated. The results show that there is a decrease in both Vmax and Km values in the presence of Psidium guajava leaf extract. The decreased Vmax and Km seen with Psidium guajava indicates that Psidium guajava binds to other alternative sites rather than the active site of the ACE and hence the inhibition is uncompetitive. The decreased Vmax/Km value indicates decreased catalytic affinity of enzyme–substrate due to the presence of the inhibitor Psidium guajava leaf extract. From these it is concluded that Psidium guajava leaf extract inhibit human serum–ACE uncompetitively and it has hypotensive effects in human.