In vitro antimicrobial activities of bark and leaf extracts of Moringa stenopetala against mastitis causing bacterial pathogens

Abstract

Antimicrobial activities of methanolic and aqueous extracts of the bark and leaf of Moringa stenopetala (Moringaceae) were studied in vitro against major mastitis causing bacterial pathogens; Staphylococcus aureus, Streptococcus agalactiae and Streptococcus dysagalactiae. The test involved the use of agar well diffusion inhibition (AWDI) test and antimicrobial activity was determined by absence or presence of growth inhibition and measurement of inhibition zone diameter (mm) expressed as mean zone of inhibition ± standard error (MZI SE). Extract solutions were prepared at four concentrations (0.3, 0.7, 1.2 and 2.0 g/ml) using Tris buffer saline. Penicillin G (1.2 g/ml) was used as a standard drug for comparison with the test materials. The study showed significant response variation between the organisms to various concentrations of the test extracts. Growth inhibition of S. aurues was much pronounced at 0.3 g/ml of methanolic extract of the bark (MZI ± SE = 58.4 ± 2.4). Conversely, S. agalactiae and S. dysagalactiae exhibited significantly (p < 0.0005) higher degree of sensitivity to methanolic bark extract at 2.0 g/ml (54.0 ± 2.1 and 50.3 ± 0.7, respectively). Similarly, methanolic leaf extract showed a more significant (p < 0.0005) growth inhibition effect on S. aurues than on S. agalactiae and S. dysagalactiae. For aqueous extracts of bark and leaf, however, the variation in growth inhibition between test organisms was observed only at 2.0 g/ml. Bark and leaf extracts of M. stenopetala were demonstrated to have a potent microbial growth inhibition effects when tested in vitro against the major bacteria causing udder infection. Further in vitro studies, determination of optimal dose and identification of active ingredients were recommended.

Keywords: antimicrobial activity, mastitis, Moringa stenopetala, moringaceae, bark and leaf extracts

Ethiopian Pharmaceutical Journal Vol. 23 2005: 15-22