Kunzea ambigua (Sm.) Druce and Kunzea flavescens C.T. White and W.D. Francis Essential Oils Inhibit the Growth of Some Bacterial Triggers of Inflammatory Diseases

Introduction: Kunzea ambigua (Sm.) Druce and Kunzea flavescens C.T. White and W.D. Francis are endemic Australian plants. Decoctions, infusions and essential oils produced from the leaves were used traditionally to treat a variety of bacterial diseases. Despite this, these species have not been rigorously examined for antibacterial properties against many pathogens. Methods: The antimicrobial activity of K. ambigua and K. f lavescens essential oils and a K. ambigua hydrosol was investigated by disc diffusion and liquid dilution MIC assays against a panel of pathogenic bacteria. Toxicity was determined using the Artemia franciscana nauplii bioassay. Results: K. ambigua and K. flavescens essential oils displayed noteworthy growth inhibitory activity against A. baylyi, K. pneumonia, P. mirabilis and P. aeruginosa (MIC values substantially <1000μg/mL). Indeed, MIC values as low as 33μg/mL were noted against P. aeruginosa. Noteworthy growth inhibitory activity was also noted for the K. ambigua hydrosol against A. baylyi and P. aeruginosa. All extracts were determined to be non-toxic in the Artemia franciscana nauplii bioassay, indicating their safety for internal use as well as for topical uses. Conclusion: The lack of toxicity of the Kunzea spp. extracts and their growth inhibitory bioactivity against a panel of pathogenic bacteria partially validate the traditional usage of these species to treat bacterial diseases and indicate their potential in the development of antiseptic agents.