In vitro assessment of bioactive components of Mirabilis jalapa ethanolic extract on clinical isolates of Salmonella typhi and Bacillus cereus

Abstract

We investigated the effects of bioactive components of ethanolic leaf extract of Mirabilis jalapa on the disease causing enteric pathogens by testing their activity against Salmonella typhi and Bacillus cereus at an initial stock solution of 20 mg/ml of the crude extract. Following serial dilutions of stock solution, and the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the crude extract, bioautography technique was used to identify bioactive fractions present in the crude extract. The observed fraction active against both organisms was separated and the MIC and MBC determined. Zones of inhibition for the crude extract at 20 ug/L were 34.33 mm±1.70 and 51.33 mm±1.88 for S. typhi and B. cereus, respectively while the zones of inhibition of separated bioactive fraction at 3mg/ml were 40.33 mm±1.33 and 40.67 mm±1.70 respectively. The MIC and MBC of the bioactive fraction showed increased in efficacy against the organisms as compared to that of the crude extract. Fourier transform infrared spectroscopy (FTIR) and gas chromatography mass spectrometry (GC-MS) analyses of the bioactive fraction were carried out on the analyte under investigation to identify the constituents of the separated bioactive fraction. The results suggest that the antibacterial activity of the plant extract may be attributed to the alkaloids present.

Key words:Bioassay, bioautography, enteric pathogens, analyte, alkaloids.