Aims:  This study aims to bring some information about the mechanism of the fungicidal action of thymol and eugenol; phenolic major components of thyme and clove essential oils respectively. Saccharomyces cerevisiae was used as yeast model. Methods and Results:  Treatment of yeast cells with these components led to their lysis as shown by the release of substances absorbing at 260 nm. In addition, scanning electron microscope observations revealed that the surface of the treated cells was significantly damaged. Conclusions:  Antifungal activity of thymol and eugenol involve alteration of both membrane and cell wall of the yeast. Significance and Impact of the Study:  This work is a preliminary contribution aiming to develop a new generation of efficient and natural antifungal agents.

The in vitro results indicated that both carvacrol and eugenol exerted an anticandidal effect by a mechanism implicating an important envelope damage. Their in vivo efficacy on experimental oral candidiasis leads us to consider them as possible antifungal agents.

Carvacrol and eugenol, the main (phenolic) components of essential oils of some aromatic plants, were evaluated for their therapeutic efficacy in the treatment of experimental oral candidiasis induced by Candida albicans in immunosuppressed rats. This anticandidal activity was analyzed by microbiological and histopathological techniques, and it was compared with that of nystatin, which was used as a positive control. Microbiologically, carvacrol and eugenol significantly (p<0.05) reduced the number of colony forming units (CFU) sampled from the oral cavity of rats treated for eight consecutive days, compared to untreated control rats. Treatment with nystatin gave similar results. Histologically, the untreated control animals showed numerous hyphae on the epithelium of the dorsal surface of the tongue. In contrast no hyphal colonization of the epithelium was seen in carvacrol-treated animals, while in rats treated with eugenol, only a few focalized zones of the dorsal surface of the tongue were occupied by hyphae. In the nystatin treated group, hyphae were found in the folds of the tongue mucosa. Thus, the histological data were confirmed by the microbiological tests for carvacrol and eugenol, but not for the nystatin-treated group. Therefore, carvacrol and eugenol could be considered as strong antifungal agents and could be proposed as therapeutic agents for oral candidiasis.

Carvacrol and eugenol could be considered as promising products in the treatment of vaginal candidiasis. This work is a preliminary contribution to the development of a new generation of efficient and natural antifungal agents for curative treatment and prophylaxis.

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