Alkylphenol Activity against Candida spp. and Microsporum canis: A Focus on the Antifungal Activity of Thymol, Eugenol and O-Methyl Derivatives

In recent years there has been an increasing search for new antifungal compounds due to the side effects of conventional antifungal drugs and fungal resistance. The aims of this study were to test in vitro the activity of thymol, eugenol, estragole and anethole and some O-methyl-derivatives (methylthymol and methyleugenol) against Candida spp. and Microsporum canis. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC). The minimum fungicidal concentrations (MFC) for both Candida spp. and M. canis were found by subculturing each fungal suspension on potato dextrose agar. Thymol, methylthymol, eugenol, methyl-eugenol, anethole, estragole and griseofulvin respectively, presented the following MIC values against M. canis: 4.8–9.7; 78–150; 39; 78–150; 78–150; 19–39 µg/mL and 0.006–2.5 μg/mL. The MFC values for all compounds ranged from 9.7 to 31 µg/mL. Concerning Candida spp, thymol, methylthymol, eugenol, methyleugenol, anethole, estragole and amphotericin, respectively, showed the following MIC values: 39; 620–1250; 150–620; 310–620; 620; 620–1250 and 0.25–2.0 μg/mL. The MFC values varied from 78 to 2500 µg/mL. All tested compounds thus showed in vitro antifungal activity against Candida spp. and M. canis. Therefore, further studies should be carried out to confirm the usefulness of these alkylphenols in vivo.