Objectives: The main objective of this work was to investigate the antifungal activity of a crude extract, fractions and subfractions from Stryphnodendron adstringens (Mart.) Coville, known as 'barbatimão'.
Methods: The growth inhibition by 'barbatimão' of 103 isolates of yeasts from vaginal fluid was determined using the broth microdilution method. In addition, the effect of the most active subfraction on cell surface hydrophobicity (CSH), germ-tube formation, budding, ultrastructure and phagocytosis of Candida albicans was analysed. Fluconazole and nystatin were used as reference drugs. The cytotoxicity of 'barbatimão' to Vero cells, macrophages and red blood cells was assessed. The most active subfraction was characterized by mass and 13C NMR spectroscopy.
Results: Subfraction F2.4 had the best antifungal action at concentrations above 7.80 mg/L. Its action was similar to nystatin, and only slightly less effective than fluconazole. CSH and the capacity for adhering to Vero cells and a glass surface were lower in treated yeasts. In addition, the inhibition of formation of the germ tube, the increase in the number of buds and changes in the cell wall ultrastructure of C. albicans were also demonstrated. 'Barbatimão' extracts showed low cytotoxicity to Vero cells, macrophages and red blood cells. Subfraction F2.4 is composed of proanthocyanidin polymers of prodelphinidin and prorobinetinidin units and gallic acid of molecular weight 2114 Da.
Conclusions: The antifungal action of subfraction F2.4 on C. albicans can be attributed to condensed tannins. It is considered moderate antifungal activity. These properties of 'barbatimão' on the growth of C. albicans, putative virulence factors and its low cytotoxicity justify further studies to investigate the mechanisms of action and the possible development of a new antifungal agent.