Phytochemical screening, antibacterial activity, and isolation of bioactive compounds from methanol extract of<i>Indigofera nummulariifolia</i> (Livera) Ex. Alston (Fabaceae)

The herb Indigofera nummulariifolia, belonging to the Fabaceae family, exhibits a global distribution in tropical and subtropical regions, including Nigeria, India, Madagascar, Australia, and parts of Asia. Herein, we reported the results of phytochemical screening, antibacterial activity, and isolation and characterization of bioactive compounds campesterol INE2 and stigmasterol INE3 from the methanol extract of the plant. The crude extracts (n-hexane, dichloromethane, ethyl acetate, and methanol) was obtained by cold maceration of the pulverized plant sample. Phytochemical screening of these extracts, detected alkaloids, saponins, flavonoids, tannins, steroids, and glycosides in the methanol extract. Ethyl acetate extract tested positive for saponins, flavonoids, tannins, and steroids, while dichloromethane and n-hexane extracts tested negative for flavonoids, tannins, and steroids. All extracts exhibited antibacterial activity against Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Staphylococcus aureus, with inhibition zones ranging from 6 mm to 20 mm. Particularly, the dichloromethane extract demonstrated significant inhibition, recording an 18 mm zone against E. coli at 800 μg/mL, as well as comparable activity against S. typhi and P. aeruginosa. Further purification of the methanol extract via column chromatography resulted in the isolation of campesterol INE2 and stigmasterol INE3. The isolated compounds were characterised using FTIR and GCMS.