Antibacterial effects of the leaves and twigs of Turraea vogelii on some enteric pathogens

Abstract

Qualitative and quantitative phytochemical analysis as well as antibacterial analysis of extracts of Turraea vogelii (Hook F.) leaves and twigs on some enteric pathogens were reported in the current study. The qualitative phytochemical screening of the leaf extracts showed the presence of saponins, flavonoids, cardiac glycosides, anthraquinones, terpenoids, steroids and alkaloids. In addition, the quantitative phytochemical screening showed that the greatest percentage yield was from the methanol extract with alkaloids (8.8%) and terpenoids (8.7%) showing the highest concentrations. The antibacterial effects of hexane, ethyl acetate and methanol extracts of Turraea vogelii at concentrations 80 mg/mL, 40 mg/mL and 20 mg/mL each were studied by the pour plate method. Clinical isolates of Escherichia coli, Salmonella typhi and Proteus mirabilis (five each) obtained from University College of Health (UCH), Ibadan, Nigeria were employed as test organisms. Gentamicin was used as control at concentration of 10 µg/mL. Preliminary antimicrobial assay using only methanol showed antimicrobial activity in both leaves and twigs. Results showed that Escherichia coli was most susceptible to all extracts of the leaves while Proteus mirabilis was the least susceptible. For the twigs, Salmonella typhi was most susceptible to the hexane extract, E. coli was most susceptible to ethyl acetate extract and Proteus mirabilis was most susceptible to the methanol extract. Minimum Inhibitory Concentration (MIC) of leaves showed that its hexane extract is bacteriostatic at 40 mg/mL but at 20 mg/mL, it showed bacteriostatic activity against Proteus mirabilis. The methanol extract of the twigs had an MIC of 20 mg/mL for most of the isolates collected except the Salmonella typhi that had an MIC of 40 mg/mL. Minimum Bactericidal Concentration (MBC) of the ethyl acetate extract of leaves and methanol extract of twigs was 40 mg/mL. This study has demonstrated the antibacterial effect of leaves and twigs extracts of T. vogelii on some enteric pathogens.