Evaluation of antibacterial activity and acute toxicity of the hydroethanolic extract of Stachytarpheta angustifolia (Mill) Vahl.

The aim of this study was to evaluate antibacterial activity, acute toxicity in mice and phytochemical profiles of hydroethanolic extract of Stachytarpheta angustifolia plant. The plant S. angustifolia has attracted the attention of the researchers because of its use as an anti-infection agent. The aqueous ethanol (80%) extract of the powdered dried whole plant was obtained by maceration. The bacteria organisms tested include Shigella dysentriae (ATCC 32412), Salmonella typhi (ATCC 213415), and the following clinical isolates: coagulase-negative Staphylococcus, Staphylococcus aureus, Proteus mirabilis, Klebsiella species and Escherichia coli. Susceptibility test, acute toxicity test and phytochemical screening of the plant extract were performed using standard procedures. The results showed that the extract had a good antibacterial activity against S. aureus, S. dysentriae, coagulasenegative Staphylococcus and Proteus mirabilis. The minimum inhibitory concentration (MIC) was found to be between 11.6 and 14.0 mg/ml for the susceptible organisms. The extract exhibited minimum bactericidal concentration (MBC) of 150 mg/ml against S. dysentriae only while other susceptible tested bacteria strains required higher concentrations. The median acute toxicity value (LD50) of the extract was determined to be 8.721 g/kg body weight indicating the extract as being slightly toxic. The extract contained triterpenoid saponins as the major bioactive constituent.