Anticandidal Activities of Selected Thai Plant Extracts and Essential Oils Against Oral Candidiasis Candida spp. Isolates

The antifungal properties of 13 ethanol plant extracts (PE) and 6 essential oils (EO) of Thai traditional herbs were screened for their anti-Candida activity against a standard strain of Candida albicans ATCC 10231 using agar disk diffusion and broth microdilution methods. Two PE, Piper betle and Alpinia galanga extracts, showed the lowest MIC and MFC values against C. albicans of 0.313 mg/mL and 0.625 mg/mL, and three EO; cinnamon bark oil exhibited the lowest MIC and MFC value of 0.039 mg/mL, followed by lemongrass oil and clove bud oil. The main compounds of these EO and PE were identified using gas chromatography–mass spectroscopy (GC-MS). The major compounds were geranial (42.7%) and neral (22.2%) in lemongrass oil, eugenol (85.5%) in clove bud oil, cinnamaldehyde (80.6%) in cinnamon bark oil, 4-allyl-1,2-diacetoxybenzene (29.5%) and hydroxychavicol (24.8%) in P. betle extract, and 1’-acetoxychavical acetate (78.0%) in A. galanga extract. All EO and PE showed antifungal activity against three oral candidiasis isolates, including C. albicans R01, C. krusei, and C. dubliniensis, with MIC/MFC ranging from 0.156 – 5.000 mg/mL. The checkerboard dilution method revealed that the combination of EO and PE showed an additive effect on C. albicans R01. In conclusion, the combination of EO with PE lowered the MIC of each agent, which could lead to decreased side effects, and hence this combination could be a promising treatment alternative for oral candidiasis.