Anthraquinones from Aloe spp. inhibit Cryptococcus neoformans sensu stricto: effects against growing and mature biofilms.

This study aimed to evaluate the in vitro effect of aloe emodin, barbaloin and chrysophanol on growing and mature biofilms of Cryptococcus neoformans sensu stricto. The compounds were added at the moment of inducing biofilm growth or after growth for 72 h to evaluate their effects on growing and mature biofilms, respectively. Then, biofilm biomass was evaluated by crystal violet staining and metabolic activity by the XTT reduction assay. Morphological alterations were also evaluated by laser scanning confocal microscopy. Aloe emodin and barbaloin affected growing biofilms and disrupted mature biofilms, reducing metabolic activity by > 60% and biomass by > 70%. Chrysophanol only inhibited mature biofilms, but to a lesser extent. In conclusion, anthraquinones, especially aloe emodin and barbaloin, show a relevant effect against growing and mature biofilms of C. neoformans sensu stricto.

Antifungal effect of anthraquinones against Cryptococcus neoformans: detection of synergism with amphotericin B.

The emergence of tolerant Cryptococcus neoformans strains to antifungals has been described. It has directed researchers to screen for new antimicrobial compounds. In this context, several plant-derived compounds, such as anthraquinones (aloe emodin, barbaloin, and chrysophanol), have been investigated for their antimicrobial properties. This study aimed to evaluate the in vitro effect of aloe emodin, barbaloin and chrysophanol on C. neoformans in vitro growth. In addition, the interaction between these anthraquinones and amphotericin B and itraconazole was evaluated. Initially, the minimum inhibitory concentrations (MIC) of these compounds were determined against 17 strains of C. neoformans by the broth microdilution method and then pharmacological interaction assays were performed with 15 strains by the checkerboard method. Aloe emodin, barbaloin, and chrysophanol showed minimum inhibitory concentrations of 236.82-473.65 µM (64-128 µg/mL), 153-306 µM (64-128 µg/ml) and ≥1007 µM (≥256 µg/ml), respectively. Furthermore, aloe emodin (11/15), barbaloin (13/15), and chrysophanol (12/15) showed pharmacological synergism (FICI < 0.5) with amphotericin B at subinhibitory concentrations (MIC/4). The itraconazole-aloe emodin interaction was additive (1/15) (0.5 < FICI < 1.0). The itraconazole-barbaloin interaction were synergistic (2/15) and additive (5/15); whereas itraconazole-chrysophanol interactions were additive (2/15). Anthraquinones, especially aloe emodin and barbaloin, present in vitro antifungal activity against C. neoformans and potentiate the antifungal activity of amphotericin B.

In vitro inhibitory effect of statins on planktonic cells and biofilms of the Sporothrix schenckii species complex.

Introduction. Sporotrichosis, caused by species of the Sporothrix schenckii complex, is the most prevalent subcutaneous mycosis in many areas of Latin America. Statins are a class of drugs widely used for lowering high sterol levels through their action on 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme in the synthesis of sterol.Aim. In this study, the antifungal activity of statins (simvastatin, atorvastatin, pravastatin) against planktonic cells and biofilms of S. schenckii complex species was evaluated, as well as the interaction of pravastatin with classical antifungals (amphotericin B, itraconazole, terbinafine).Methodology. Eighteen strains of Sporothrix species were used. The antifungal susceptibility assay was performed using the broth microdilution method. Mature biofilms were exposed to statins and metabolic activity was measured by the XTT reduction assay.Results. MICs of statins ranged from 8 to 512 µg ml-1 and from 8 to 256 µg ml-1 for filamentous and yeast forms, respectively. Regarding mature biofilms, MICs of 50 % inhibition (SMIC50) were 128 µg ml-1 for simvastatin and atorvastatin and >2048 µg ml-1 for pravastatin. MICs of 90 % inhibition (SMIC90) were 512 µg ml-1 for simvastatin and >2048 µg ml-1 for atorvastatin and pravastatin.Conclusion. These results highlight the antifungal and antibiofilm potential of statins against S. schenckii complex species.

Antifungal activity of different molecular weight chitosans against planktonic cells and biofilm of Sporothrix brasiliensis.

Sporotrichosis, caused by Sporothrix schenckii complex species, is the most prevalent subcutaneous mycosis in many areas of Latin America. Chitosan has been used as an antifungal agent; however the effects of the molecular weight (MW) of chitosan (i.e. high (HMW), medium (MMW) and low (LMW) molecular weight chitosan) on S. brasiliensis has not been well described, particularly on biofilms. Effects on the planktonic form activity of S. brasiliensis were quantified by broth microdilution, while anti-biofilm activity was quantified by measuring metabolic activity via XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide and biomass formation (crystal violet). The molecular weight of chitosan modulated its effect on the planktonic form of S. brasiliensis, presenting lower MIC values for LMW chitosan. With regards both the adhesive and mature phases of biofilm, the LMW chitosan reduced biomass and metabolic activity most effectively. This study confirms the effects of the molecular weight and deacetylation degree of chitosan on its antifungal properties for potentially pathogenic fungi.