Indigenous South African essential oils as potential antimicrobials to treat foot odour (bromodosis)

Abstract

Foot odour, known as bromodosis, is produced as a result of a combination of exocrine secretions and bacterial growth on the feet. Several commercial essential oils have demonstrated promise in inhibiting the growth of odour-causing bacteria as a novel strategy to offer relief from this dermatological problem. South Africa harbours an abundance of diverse indigenous flora which has shown favourable antimicrobial properties. As such, the potential application of natural products against bromodosis-causing Brevibacterium species with the aim of finding cosmetically appealing and promising African sourced essential oils capable of masking foot malodour was the focus of this study. The antimicrobial activity of 41 oils were investigated using the microdilution assay where the minimum inhibitory concentrations (MICs) were reported against Brevibacillus agri (ATCC 51663), Brevibacillus epidermidis (DSM 20660) and Brevibacillus linens (DSM 20425). Ninety-five percent of the oils tested displayed noteworthy activity (MIC ≤ 1.00 mg/mL) against B. agri with S. africana-caerulea demonstrating the highest activity (0.03 mg/mL) overall. Thirty-one essential oils displayed noteworthy activity (MIC ≤ 1.00 mg/mL) against B. epidermidis. Two essential oils (Plectranthus grandidentatus and Salvia africana-lutea) displayed noteworthy activity (MIC = 1.00 mg/mL) against B. linens. The major constituents for each oil was determined using gas chromatography coupled to mass spectrometry and limonene appears to be the most frequent essential oil constituent (23 of the oils). The olfactory properties of the essentials oils displaying noteworthy activity were further considered. These findings presenting interesting anti-bromodosis activity hold great potential, as not only do the selected oils have antimicrobial activity, but the pleasant aroma of these aromatic botanicals can further mask and control foot odour.