Lindiwe Mpala1, Getmore Chikowe1, Ian Edwin Cock1,2,*
1School of Environment and Science, Griffith University, 170 Kessels Rd, Nathan, Brisbane, Queensland, AUSTRALIA.
2Environmental Futures Research Institute, Griffith University, 170 Kessels Rd, Nathan, Brisbane, Queensland, AUSTRALIA.
Introduction: Xanthophyllum fragrans C.T. White is a rainforest tree that is native to north-eastern regions of Australia. X. fragrans leaf extracts were examined for the ability to inhibit the growth of Pseudomonas aeruginosa. Methods: The antimicrobial activity of a methanolic X. fragrans leaf extracts were investigated by disc diffusion and growth time course assays against P. aeruginosa. The growth inhibitory activity was further quantified by MIC determination. Toxicity was determined using the Artemia franciscana nauplii bioassay. Results: The methanolic X. fragrans leaf extract was a potent inhibitor of P. aeruginosa growth (MICs of 430 and 1687μg/mL against the reference and clinical strains respectively). The aqueous X. fragrans leaf extract was also a moderate inhibitor of P. aeruginosa growth (MICs approximately 1000 and 2500μg/mL against the reference and clinical bacterial strains respectively). The antibacterial activities of the methanolic X. fragrans leaf extracts were further investigated using growth time course assays that showed significant growth inhibition in cultures of P. aeruginosa within 1 h of exposure. All extracts were determined to be non-toxic in the Artemia franciscana nauplii bioassay, indicating their safety for use in preventing diseases caused by these pathogens. Conclusion: The lack of toxicity of the X. fragrans leaf extracts and their growth inhibitory bioactivity against P. aeruginosa indicates their potential in the development of new therapies targeting this bacterium.