Antifungal activity of tannic acid against Candida spp. and its mechanism of action.

The increase in fungal resistance is a major public health concern. In this context, Candida spp. is an important genus related to invasive diseases, especially in immunosuppressed patients. The relevance of alternative approaches to increasing fungal resistance stands out, in which products of natural origin demonstrate potential antifungal activity in vitro against Candida spp. In this sense, this work aimed to evaluate the in vitro activity of tannic acid against Candida spp. Minimum inhibitory concentration (MIC) was determined for tannic acid and the antifungals, and the checkerboard assay was performed to analyze the interactions between them. Furthermore, we evaluated the tannic acid antibiofilm activity and its possible mechanism of action. Tannic acid showed MIC ranging to 0.06 to 0.5 µg/ml and showed no loss of effectiveness when combined with antifungals. Also, is safe at the concentrations it exerts its antifungal activity in pre-formed biofilms, as demonstrated by IC50 in murine fibroblasts cells and the hemolytic assay. Additionally, its mechanisms of action can be related with induction of signals that lead to apoptosis in fungal cells.