Antifungal activity of the aqueous extract of Stachytarpheta cayennensis, (Rich.) Vahl. (Verbenaceae), on oral candida species

The objective of this study was to evaluate the antifungal activity of the aqueous extract of the leaves of the "verbena" (gervao roxo) Stachytarpheta cayennensis, (Rich.) Vahl. (Verbenaceae), by determining the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) on different species and strains of the genus Candida. In this study, the species Candida albicans, Candida tropicalis, Candida glabrata, Candida stellatoidea, Candida dubliniensis and Candida krusei were included. Four strains of C. albicans and three of C. tropicalis were used, while for the other species only one strain was tested. These yeasts were used in this study because of their importance and frequency in the oral cavity. The yeasts were subjected to treatments with concentrations of the aqueous extract ranging from 0.09 to 25 mg mL-1. The results indicated, however, that concentrations of less than 12.5 mg mL-1 were insufficient to show a fungistatic or fungicidal effect. The concentration of 12.5 mg mL-1  showed a fungistatic effect on most tested strains and species, C. albicans CαFB-12 and ATCC-44858; C. tropicalis CTFB-22 and CTFB29. The fungicidal effect (MFC) was observed only on the species C. krusei for the concentration of 12.5 mg mL-1. Based on the employed methodology, it is concluded that the aqueous extract of S. cayennensis showed an antifungal, mainly fungistatic, effect on oral Candida species.   Key words: Yeasts, candidiasis, metabolites, Stachytarpheta cayennensis.