Evaluation of Antimicrobial Effect of a Skin Formulation Using Different Combinations of Selected Herbal Essential Oils

Abstract

Background: Microbial resistance is a global health concern, prompting the development of new antimicrobials. Most essential oils (EOs) have good antimicrobial properties. Hence EOs can be used as alternatives to combat antimicrobial resistance. Objective: To evaluate the antimicrobial effect of a skin formulation using different combinations of selected herbal EOs Methods: Based on detailed literature review five EOs (cinnamon bark, clove, citronella, nutmeg and eucalyptus) with good antimicrobial activity were selected. Their antimicrobial activity was tested against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans using disc diffusion assay and micro broth dilution method. Positive controls for bacteria and fungi were Gentamycin IV and Fluconazole IV injections respectively. Two EOs combination ratios (ratio 1- equal volume from each oil, ratio 2- equal volume from cinnamon, clove, and citronella oil) were selected and their antimicrobial activity was evaluated using the disc diffusion assay. Based on the results creams were formulated and their antimicrobial activity was measured using the well diffusion assay. The creams were evaluated for physical stability for one month period. Results: All five EOs showed inhibitory activity against tested strains. Cinnamon oil showed the highest activity against Candida albicans (35.33mm±0.57, 3.351mg/mL), while nutmeg oil showed the lowest activity against Pseudomonas aeruginosa (9.66mm±1.52). Cinnamon oil and positive control showed no significant antimicrobial activity against Candida albicans (p>0.05) while the positive control had significant antimicrobial activity against other organisms (p<0.05). Both ratios showed a synergistic effect against Staphylococcus aureus (21.33mm±0.57, 29.00mm±1.00) and an antagonistic effect against Candida albicans (20.33mm±0.57, 18.66mm±0.57). Both formulated creams have shown good antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans and they were stable under tested parameters. Conclusions: Combinations of cinnamon bark, clove, citronella, nutmeg, and eucalyptus oils can create effective antimicrobial creams making a potential solution for combating antimicrobial resistance and treating skin infections.