Antimicrobial Activity of Lemongrass, Citronella and Manila Elemi Essential Oils in Liquid and Vapor Phase

Abstract

The antimicrobial activities of lemongrass (Cymbopogon citratus), citronella (Cymbopogon nardus) and Manila elemi (Canarium luzonicum) essential oils were determined on six bacterial species, namely: Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa', and one fungal species, Candida albicans through liquid and vapor contact. To determine the minimum inhibitory concentration (MIC) of the three essential oils in their liquid and vapor phases, an agar dilution assay and modified box-vapor assay were used, respectively. Concentrations ranging from 7.8 mg/mL to 125mg/mL were prepared from these essential oils. Results showed that the antimicrobial activity of the vapor phase was found to be significantly higher than its liquid phase (P = 0.001) with a 95% confidence level. However, the antimicrobial activities of lemongrass and citronella oils did not show a significant difference (P = 0.719), due to their active components citral and citronellal, respectively, which both belong in the aldehyde group. Nevertheless, mean values of MIC for the liquid phase was lowest for lemongrass oil (21.267 mg/mL) while the mean values of MIC for the vapor phase were the lowest for citronella oil (23.862 mg/mL). Lemongrass is more soluble than citronella thus it exhibited a higher antimicrobial activity in its liquid phase. Citronella is more volatile than lemongrass thus it exhibited a higher antimicrobial activity in its vapor phase. Antimicrobial activity of lemongrass and citronella oils was found to be significantly higher than that of Manila elemi oil with the values of P = 0.027 and P = 0.004, respectively. This is due to limonene, a weak active component of elemi oil. Hydrocarbons, like limonene, have lower antimicrobial activities than aldehydes, such as citral in lemongrass and citronellal in citronella.