Antimicrobial and antioxidant activities of extract and fractions of the African yam bean (Sphenostylis stenocarpa) Seed

The African yam bean (AYB) (Sphenostylis stenocarpa) is a medicinal plant that has poorly been researched on. It is a member of the leguminous crop belonging to the Fabaceae family. AYB's potential therapeutic qualities make it a candidate for drug discovery. This study was carried out to ascertain the pharmacological properties of the extracts. Ethanolic extract and fractions of AYB seed were tested on selected microorganisms: Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella spp, Escherichia coli, and Candida albicans using agar well diffusion assay, and evaluated for their potential to scavenge free radicals adopting Ferric reducing antioxidant power (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assays, and finally subjected to phytochemical analysis using standard procedures. The crude extract and fractions produced dose-dependent and broad-spectrum antimicrobial activity. The inhibition zones and minimum inhibitory concentration also varied across the test organisms having 2 - 6 mm and 12.5 – 100 mg/ml respectively. The ethylacetate fraction was observed to be the most active extract. The crude extract and fractions produced a moderate capacity to scavenge free radicals by generating Diphenylpicrylhydrazine (reduced) through the conversion of DPPH as indicated. Phytoactive constituents such as alkaloids, tannins, flavonoids, steroids, terpenoids, and saponins detected in the crude extract and fractions may be responsible for the pharmacological activities recorded. The result of this study further validates the possibility of identifying a lead in the extract of AYB with therapeutic potentials.