Angiotensin-converting enzyme and renin inhibition activities, antioxidant properties, phenolic and flavonoid contents of Cuphea ignea A. DC

Cuphea ignea A. DC. is an ornamental plant belonging to family Lythraceae distributed in the tropics and temperate zones. Some Cuphea members are traditionally used in treatment of hypertension. The aim of this research was to study the antihypertensive activity of the plant by applying a bio-guided fractionation scheme of the leaves, stems, and flowers using in vitro angiotensin-converting enzyme (ACE) and renin inhibition assays to identify the active organ and its respective active fractions. The aqueous extract and the n-butanol fraction of the leaves showed the highest ACE inhibition activity with IC50 values 0.491 and 0.084 mg/mL, respectively. The renin inhibition activity showed that the alcoholic extract of the leaves had the highest percentage of inhibition (94.82%). Meanwhile, the methylene chloride fraction of the stems showed the highest renin inhibition activity (98.14%) followed by the ethyl acetate fraction of the leaves (93.09%). The antioxidant activity was tested using the 2,2-diphenyl-1-picrylhydrazyl and oxygen radical absorbance activity assays. Correlation studies of the antioxidant activity showed moderate correlation with the phenolic content and strong correlation with the flavonoid content. The renin inhibition activity showed significant positive correlation with the phenolic and flavonoid contents with r values (0.777 and 0.629, respectively).