The effects of three Thai herbal essential oils against Candida biofilms

The purpose of this study was to determine the effects of three Thai herbal essential oils used in aromatherapy, namely lemongrass (Cymbopogon citratus DC), holy basil (Ocimum sanctum L.) and kaffir lime (Citrus hystrix DC), against Candida biofilms and compare those effects with nystatin. Employing a formazan salt reduction assay, the results showed that among the three essential oils, kaffir lime oil exhibited the lowest sessile minimum inhibitory concentration (SMIC), followed by lemongrass oil and holy basil oil, respectively. The SMIC of nystatin, kaffir lime, lemongrass and holy basil oil at 50% inhibition (SMIC₅₀) on Candida albicans were 0.032, >0.93– <1.86, 3.46 and 7.93mg/ml, respectively, while the SMIC at 90% inhibition (SMIC₉₀) were 0.5, 1.8, 13.8 and 31.7mg/ml, respectively. The SMIC₅₀ of nystatin, kaffir lime, lemongrass and holy basil oil on Candida krusei were 0.02, 0.9, 1.7 and 4.0mg/ml, respectively, while the SMIC₉₀ were 0.5, 1.9, 6.9 and 31.7mg/ml, respectively. Overall, the data demonstrated that the three essential oils can inhibit the growth of C. albicans and C. krusei biofilms although the SMIC₅₀ and SMIC₉₀ of those three essential oils were higher than nystatin.

Acknowledgements: This work was supported by grants from the Faculty of Dentistry, Khon Kaen University and the Thailand Research Funds (grant No RDG 5020022).