Phytochemicals, antioxidant and antimalarial activity of the leaves and stem bark extracts of Sterculia setigera del. (Sterculiaceae)

Abstract

Medicinal plants are widely recognised for their therapeutic applications such as the treatment of malaria, diabetic, hypertension and bleeding etc. The leaves and stem bark fractions of Sterculia setigera were investigated for their metabolic profile (phytochemical screening), antioxidant activity (DPPH assay) and antimalarial activity against Plasmodium falciparum. Results of the antioxidant and antimalaria assays were compared with standards (i.e, ascorbic acid/gallic acid and artesunate respectively). The phytochemical analysis of the plant parts revealed the presence of vital antioxidant and antimalarial constituents that support the ethnomedicinal use of the plant. Both the leaves and stem barks displayed the presence of alkaloids, flavonoids, steroids and reducing sugar, while tannin was only observed in the leaves of the plant. The ethanol extract of the leaves showed the highest antioxidant activity (IC₅₀=13.78 µg/ml) compared to standards ascorbic acid (IC₅₀=11.28 µg/ml) and gallic acid IC₅₀=25.52 µg/ml). Additionally, the ethanol extract (LE1) and ethyl acetate extract (LE1-03) of the leaves of the plant displayed a highest antimalaria activity with a percentage elimination of the parasite of 80 % at 100 µg/ml and 88 % at 1000 µg/ml respectively compared to the control 94 % at 1000 µg/ml. These activities observed in the extract is correlated with the phytochemicals present in the extracts of the plant parts. The isolation and identification of the specific bioactive compounds that are responsible for the antioxidant and antimalaria activity is recommended.