Resumo

Cryptococcosis is a disease caused by encapsulated yeasts and is a major cause of mortality, especially in HIV positive patients. The two main species responsible for this disease are Cryptococcus neoformans and Cryptococcus gattii. The number of available antifungal agents is limited and many of them are ineffective and toxic, a fact which, added to the emergence of strains resistant to available drugs, means there is a need for discovery of new antifungal drugs and plant extracts are attractive prototypes for this purpose. The aim of this study was to evaluate the antifungal activity of gallic acid and its derivatives, methyl gallate and ethyl gallate, against ATCC 90012 strain and three clinical isolates C. neoformans. The clinical isolates were characterized as susceptible (26), intermediate (27) and resistant (30), in vitro, to fluconazole (FLU).Two parrots isolates of C. gattii, a susceptible and a reduced sensitivity (118) to FLU. The determination of minimum inhibitory concentration (MIC) was obtained by microdilution according to the EUCAST (European Committee on Antimicrobial Susceptibility Testing) document EDef 7.2 (2008), with modifications. The drugs Fluconazole and amphotericin B were used as control test. The MIC of gallic acid was 31.25 mg/L for C. neoformans ATCC 90012 and 15.63 mg/L for the other clinical isolates. The of methyl and ethyl gallate were only significant for the clinical isolates of C. gattii resistant and susceptible to fluconazole. The methyl and ethyl gallates showed a MIC of 7.81 mg/L and 15.63 mg/L respectively, for the isolates resistant to fluconazol, and for the clinical isolates susceptible to fluconazol, were 3.91mg/L. These results suggest that these gallic acid extracts and derivates may be a potential source of new agents for the treatment of cryptococcosis.