Eucalyptus major (Maiden) Blakely Leaf Extracts Inhibit the Growth of Axillary and Foot Odour Producing Bacteria

Aiden Wood¹, Ian Edwin Cock^{1, 2,*}

¹School of Environment and Science, Nathan Campus, Griffith University, Brisbane, AUSTRALIA.

²Centre for Planetary Health and Food Security, Nathan Campus, Griffith University, Brisbane, AUSTRALIA.

DOI: 10.5530/pc.2025.1.3

ABSTRACT

Introduction: Eucalyptus spp. extracts inhibit the growth of many bacterial pathogens. They may also inhibit the growth of malodour producing bacteria and thus be useful deodorant components, although this is yet to be tested. Materials and Methods: Methanolic and aqueous Eucalyptus major (Maiden) Blakely leaf extracts were investigated by disc diffusion and liquid dilution MIC assays against the most significant bacterial contributors to axillary and plantar malodour. Toxicity was determined using the Artemia franciscana nauplii bioassay. Results: Methanolic and aqueous E. major leaf extracts displayed noteworthy bacterial growth inhibitory activity against all of the malodour forming bacteria tested. The methanolic extract was a particularly potent growth inhibitor, with liquid dilution (LD) MIC values of 183, 500, 500 and 125 μg/mL against C. jeikeium, P. acnes, B. linens and S. epidermidis respectively. Similar, albeit slightly higher LD MIC values were noted for the aqueous E. major leaf extract (LD MICs of 625, 625, 750 and 500 μg/mL against C. jeikeium, P. acnes, B. linens and S. epidermidis respectively). The methanolic and aqueous E. major leaf extracts were nontoxic in the Artemia fransiscana bioassay. Conclusion: The lack of toxicity of the methanolic and aqueous E. major leaf extracts and their potent growth inhibition of axillary and plantar malodour producing bacteria indicate their potential as deodorant components. Further studies are warranted to isolate and identify the active components.

Keywords: Grey gum, Myrtaceae, body odour, deodorant, Corneybacterium jeikeium, Propionobacter acnes, Brevibacter linens, Staphylococcus epidermidis.