Comparative phytochemical and antioxidant studies of the hexane and ethyl acetate fractions of the methanol extracts of the stem bark of Allophylus africanus

Abstract

This research is aimed at comparing the phytoconstituents and antioxidant activities of the methanol extract, hexane and ethyl acetate fractions of the stem bark of Allophylus africanus Beauv. for development into possible phytopharmaceuticals. About 500 g dry weight of the stem bark sample was macerated for a total of 48 h using 5 L methanol to obtain the methanol extract. The extract was fractionated into hexane and ethyl acetate and each fraction monitored using Thin Layer Chromatography (TLC). The extract and fractions were also subjected to phytochemical screening. Using the DPPH radical scavenging model, the antioxidant studies of the extract and fractions were carried out at concentrations between 1 mg and 0.00625 mg/mL. Alkaloids, carbohydrates and terpenoids were found present in all three samples while anthraquinone, tannins, phenols and steroids were not detected in all three samples of the stem bark. The crude methanol extracts and the hexane fractions of the stem bark of Allophylus africanus showed no antioxidant activity when compared to Vitamin C using the DPPH free radical scavenging activity model. However, at concentrations between 1 mg/mL and 0.0625 mg/mL a significant and dose-dependent antioxidant activity was observed with the ethyl acetate fraction of the stem bark. The enrichment of the ethyl acetate fraction with alkaloids, terpenoids and saponins, which possess anti-oxidant activity may be a plausible explanation for the observed anti-oxidant activity. The ethyl acetate fraction of the stem bark can thus be further investigated as a possible antioxidant phytopharmaceutical for the management of oxidative stress.