Resumo

Fungal infections are responsible to produce high rates of morbidity and mortality. Currently a range of fungi, before nonpathogenic, have been considered responsible for causing many diseases in humans, called opportunistic infections. These emerging fungi affect mainly immunocompromised patients and have their pathogenicity unknown. Among the drugs available for treatment, amphotericin B and fluconazole are the most commonly used in clinical practice, despite the severe side effects. Considering these facts, efforts to develop more effective therapeutic options are needed. The genus Hypericum includes several species used in traditional medicine and recognized for biological activities such as antimicrobial and anticancer, among others. Thus, the aim of this work was to evaluate antifungal potential of lipophilic extracts of three Hypericum species native to South Brazil: Hypericum carinatum Griseb., Hypericum linoides A. St.-Hill. and Hypericum myrianthum Cham. & Schlecht. The dried and powdered plant materials were extracted by maceration with n-hexane at room temperature and the fractions were evaporated to dryness under reduced pressure. To evaluate the antifungal activity, many isolates of yeast fungi were utilized, including Candida albicans and Candida non- albicans species, Cryptococcus neoformans and Geotrichum candidum. The susceptibility of these isolates to extracts was assessed by the CLSI broth microdilution method with slight modifications. The most promising results were obtained with C. neoformans, strain CRY 14, reaching minimum inhibitory concentrations of 125 µg/mL, 250 µg/mL and 15.6 µg/mL to H. carinatum, H. linoides and H. myrianthum, respectively. These results could be explained by the high amounts of dimeric phloroglucinol derivatives present in these lipophilic extracts. Besides, it is well known that this class of compounds exhibits antimicrobial effects. The current investigation demonstrated that lipophilic extracts of Hypericum species are able to inhibit the fungal activity of emerging yeasts. The main result with C. neoformans is remarkable owing to the increasing resistance of this species to antifungal agents. The activity of extracts and isolated compounds must be further investigated to evaluate the synergism with, medicines already utilized in therapeutic, their toxicity and presumable action mechanism.