Antimicrobial activity of the various plant parts of Warburgia salutaris

Warburgia salutaris (G. Bertol.) Chiov. is an aromatic plant found in forests and ravines of northern KwaZulu-Natal, Swaziland, Mpumalanga and the Northern Province of southern Africa. The vernacular names for this tree is Ishibhaha (Zulu), Shibaha (Tsonga), pepper bark tree and Peperbasboom (Afrikaans). Although the bark has a variety of uses, it is mainly used as an expectorant and for the treatment of upper respiratory tract infections. The aim of this study was to determine or confirm the antimicrobial activity of the bark, roots and leaves when exposed to a host of pathogens. Water and methanol/chloroform extracts were prepared and tested against the selected pathogens using minimum inhibitory concentrations (MIC) and then determining possible antibiofilm activity using the crystal violet assay. The majority of the extracts were effective against Mycobacterium smegmatis with the solvent root extract exhibiting the noteworthy antimicrobial activity (MIC of 0.25mg/ml). The bark (water extract) had antimicrobial activity within the MIC range of 1.00–2.00mg/ml) against most of the pathogens while the MIC's of the methanol/chloroform extract of the root ranged between 0.25 to 4.00mg/ml. None of the extracts showed more than fifty percent inhibition of a 24 hour biofilm.