In vitro antioxidant, anti‐inflammatory and antihypertensive activities of methanol leaf extract of Peasea americana

Abstract

Hypertension is a cardiovascular disease of remarkable health and economic importance. Management of hypertension with orthodox medicine is associated with side effects and is unaffordable to a larger percentage of people in Africa. P. americana leaf extract (PALE) is commonly used in the management of hypertension in Nigeria trado‐medicine. In this study, we investigated the antioxidant, anti‐inflammatory and anti‐hypertensive activities of the crude methanol extract, fractions and phytochemicals of P. americana leaf. The in vitro‐antioxidant assays were carried out to evaluate the free radicals scavenging activities of PALE on 1, 1‐diphenyl‐2‐picrylhydroxyl (DPPH), 2, 2‐azenobis‐3‐ethyl benzothiozoline‐6‐sulfonic acid (ABTS), hydroxyl and nitric oxide radicals. In addition, metal chelating and ferric reducing power assay were done. Anti‐inflammatory activities were evaluated using 15‐1ypoxygenase enzyme inhibition assay. Absorption were read spectophotometrically and 1C50 was calculated using a standard calibration curve. Phytocompound isolation was by extract fractionation, column, thin layer and preparatory thin layer chromatography. Crude methanol extracts, N‐hexane, ethyl acetate, chloroform, N‐butanol and aqueous methanol fractions had significantly higher anti‐oxidant activities when compared with gallic acid. There anti‐inflammatory activity is comparable to that of Indomethacin and antihypertensive activity for PALE (with IC50 of 135.99±10.06) is significantly lower when compared with captopril (with IC50 41.86±2.10). Four pure phytochemicals were isolated and named LEACA, LEACB, LEACC, and LEACD. The isolated compounds had significantly higher antioxidant activities on DPPH, ABTS, and hydroxyl and nitric oxide radicals when compared with gallic acid. The anti‐hypertensive activities of the isolated phytocompounds from the ethyl acetate fraction of the leaf were significantly higher (with IC50 of 24.83±0.63, 9.48±1.45, 2.79±1.35 and 1.59±0.48 respectively) than that of captopril (with 1C50 of 41.89±2.10). The result obtained from this study suggest that P. americana leaf has free radical scavenging and antioxidant activities, anti‐inflammatory and anti‐hypertensive activities and can ameliorate oxidative stress, and inflammation associated with hypertension.