Abstract
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.
Highlights
Dermatophytosis is the most important superficial mycoses in both humans and animals
The present research was carried out to evaluate the antifungal activity of alkylphenols and O-methyl-derivatives of thymol and eugenol (Figure 1) against Candida spp. and M. canis in vitro
Many essential oils exhibit antioxidant and antimicrobial activities. Phenols, such as thymol, carvacrol, and eugenol, are among the most active natural antioxidants and antimicrobials found in essential oils
Summary
Dermatophytosis is the most important superficial mycoses in both humans and animals. Antifungal resistance in Candida spp strains has been observed in both humans and animals [5,6,7]. Our previous studies with essential oils from species of Crotons [10] and Lippia sidoides [8] have shown their antifungal activity against Candida spp. and M. canis. In the GC/MS analysis of these oils, the main constituent found in the essential oil of L. sidoides was thymol, while in the essential oil of Croton nepetaefolius this was methyleugenol and for Croton zenhtneri its was estragole/anethole. Based on these studies, the present research was carried out to evaluate the antifungal activity of alkylphenols (thymol, eugenol, estragole and anethole) and O-methyl-derivatives of thymol and eugenol (Figure 1) against Candida spp. and M. canis in vitro. The O-methyl-derivatives were obtained by reaction of the phenolic group with dimethyl sulfate in alkaline medium [13]
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