A Comparative Investigation of the Antimicrobial Properties of Indigenous South African Aromatic Plants with Popular Commercially Available Essential Oils

Abstract

Essential oils have been accepted and recognized as having several therapeutic applications. Popular commercial oils such its lavender, rosemary, tea tree, thyme and peppermint have been used extensively in aromatherapy and as a treatment regimen against bacterial and fungal infections. Extensive studies on indigenous essential oils used in South African traditional healing rites indicate efficacy against a number of pathogens. By means of comparatively determining the MIC of the above-mentioned popular commercial oils against the essential oils of five indigenous plants (Myrothamnus flabellifolius, Osmitopsis asteriscoides, Heteropyxis natalensis, Artemisia afra and Lippiajavanica), efficacy was determined against eight bacterial reference strains and two yeast reference strains. The laboratory conditions and inoculum were standardized to ensure all 10 essential oils (commercial and indigenous) were evaluated under identical conditions. Where MIC data indicated coinciding values between commercial and indigenous oils, the MIC was further refined to narrow the increments. To comparatively demonstrate the time kill efficacy, commercial and indigenous oils were exposed to Staphylococcus aureus, Klebsiella pneumoniae and Candida albicans and the cidal efficacy plotted over time against the logarithm of viable colonies. Results indicate that South African indigenous essential oils compare favorably with commercial oils studied herein. Of all oils studied, Myrothamnus flabellifolius showed the most rapid cidal effect against all three pathogens tested.