Potencial anti-Candida albicans dos extratos etanólico e aquoso das folhas de Bauhinia holophylla (Bong.) Steud

Abstract

Oral candidiasis is a fungal infection caused mainly by Candida albicans, considered a public health problem that affects a large part of the population. Candida albicans inhabits the normal human microbiota commensally, however, an imbalance in the host organism can cause a transition from the commensal to the pathogenic stage. In addition, topical therapy for this infection is restricted to the use of the antifungals chlorhexidine gluconate and nystatin, but these have associated cytotoxic and adverse effects. Faced with the need to supply limited antifungal therapy, medicinal plants are a rich possibility for the development of antifungal agents capable of acting in the treatment of oral candidiasis. Bauhinia holophylla Bong. Steud. known as "pata-de-vaca" belongs to the Fabaceae family and is popularly used to treat infections and inflammatory processes, however, its antifungal potential is still poorly understood. The aim of this study was therefore to evaluate the chemical composition and antifungal activity of the ethanolic and aqueous extracts of Bauhinia holophylla (Bong.) Steud. against Candida albicans. The extracts were subjected to scanning analysis in the ultraviolet region (UV/Vis), qualitative analysis of secondary metabolites and Ultra Efficiency Liquid Chromatography with a diode array detector. The antifungal activity of EEB and AEB was determined using the broth microdilution technique, as well as the mechanisms of action via sorbitol and ergosterol. The Checkerboard method was used to determine the combination of extracts with chlorhexidine gluconate, nystatin and fluconazole. Growth kinetics were performed using the viable cell counting method expressed in cells/mL. The formation of germ tubes was evaluated by counting in a Neubauer chamber under an optical microscope. Antibiofilm activity was determined by viable cell counting and the XTT method. Finally, hemolytic activity was evaluated in human erythrocytes and quantified using a spectrophotometer. The results showed the presence of protocatechuic acid, epicatechin and rutin in both extracts. EEB showed antifungal activity with MIC of 15.68 µg/mL and AEB 31.25 µg/mL against C. albicans ATCC 90028, ATCC 10231 and against the six oral isolates with MIC between 7.8 – 62.5 µg/mL. The sorbitol and exogenous ergosterol assays suggest that EEB and EAB possibly bind to the ergosterol present in the fungal cell membrane. EEB showed a synergistic effect with chlorhexidine gluconate, nystatin and fluconazole and AEB with nystatin and fluconazole. In the growth kinetics assay, treatments with EEB and fluconazole exhibited a similar reduction. The extracts did not show activity on the formation and destruction of biofilms. In the formation of germ tube by C. albicans, EEB, AEB showed a percentage reduction in germination of 29% and 31%, respectively, and fluconazole of 24%. Both extracts did not show a hemolytic percentage in human erythrocytes. The results found showed promising activities of the extracts from the perspective of controlling C. albicans, especially with regard to oral candidiasis.