Ent-hardwickiic acid from C. pubiflora and its microbial metabolites are more potent than fluconazole in vitro against Candida glabrata

Abstract

The incidence of Candida glabrata infections has rapidly grown and this species is among those responsible for causing invasive candidiasis with a high mortality rate. The diterpene ent-hardwickiic acid is a major constituent in Copaifera pubiflora oleoresin and the ethnopharmacological uses of this oleoresin by people from Brazilian Amazonian region point to a potential use of this major constituent as an antimicrobial. Therefore, the goal of this study was to evaluate the antifungal activity of ent-hardwickiic acid against Candida species and to produce derivatives of this diterpene by using microbial models for simulating the mammalian metabolism. The microbial transformations of ent-hardwickiic acid were carried out by Aspergillus brasiliensis and Cunninghamella elegans and hydroxylated metabolites were isolated and their chemical structures were determined. The antifungal activity of ent-hardwickiic acid and its metabolites was assessed by using the microdilution broth method in 96-well microplates and compared with that of fluconazole. All the diterpenes showed fungistatic effects (ranging from 19·7 to 75·2 µmol l−1) against C. glabrata at lower concentrations than fluconazole (163·2 µmol l−1) and were more potent fungicides (ranging from 39·5 to 150·4 µmol l−1) than fluconazole, which showed fungicidal effect at the concentration of 326·5 µmol l−1.