Antibacterial Activity and FTIR Characterization of subfractions from Ethylacetate Fraction of Piliostigma thonningii against some Salmonella species

Abstract

The present study deals with the antibacterial activity and functional group analysis of Piliostigma thonningii extract, its fractions, sub-fractions and column isolates. The crude methanol extract of the plant (PT1), its partitioned-soluble fractions (PT1-01, PT1-02, PT1-03 and PT1-04), sub-fractions from VLC fractionation of ethyl acetate fraction (VLC1 –VLC7) and column sub-fractions (Et1-Et6) were screened for their antibacterial potentials using agar well diffusion technique. The crude methanol leaf extract was first partitioned with different organic solvents to afford the n-hexane-chloroform- and ethyl acetate-partitioned-soluble fractions. The antibacterial active ethyl acetate – partitioned soluble fraction was further fractionated over a vacuum liquid chromatography followed by column chromatography of the antibacterial active VLC sub-fraction (VLC5). Characterization of the antibacterial active column sub-fractions was done using Fourier transform infrared spectroscopy (FTIR). The results showed that all the fractions possess antibacterial activity on at least one of the bacteria tested, however, the ethyl acetate fraction (PT1-03) exhibited the widest zone of inhibition on the test bacteria (14-16mm) at the concentration of 100mg/ml. The zones of growth inhibition increased with increasing concentration of the extracts. The corresponding increase in concentration and growth inhibition zone was significant (p<0.05). The FT-IR result of the column isolate from the ethylacetate fraction revealed the presence of phenols, aldehydes, ketones, amines, amides and carboxylic acids. The spectra of the activity exhibited by the isolates signified their potency for the development of therapeutic agents against these pathogenic bacteria.