Resumo

Introduction: Uncaria tomentosa (cat's claw) is a vine widely distributed in rainforests of South America. Cat's claw bark have been studied intensively owing antitumoral, immunostimulant, immunoadjuvant and antiviral properties, being included in the United States Pharmacopoeia recently. Also, it has been traditionally used in the treatment of rheumatic diseases, cancer, allergies, and microbial infections. The three bioactive fractions recognized include: oxindole alkaloids (FALC), polyphenols (FPOLIF), and triterpenes derivated from quinovic acid (FAQ). Objective: This work focused the antifungal activity of crude extract and fractions of U. tomentosa against pathogenic yeasts. Materials and Methods: A crude extract from its bark as well the purified fractions FALC and FAQ, previously obtained by solid-phase fractionation technique, and FPOLIF fraction, obtained by precipitation, were prepared for that intend specifically. The contents of triterpenes and pentacyclic oxindole alkaloids were determined by HPLC-DAD. The total polyphenols content was estimated through Folin Ciocalteau assay. For testing antifungal screening, the determination of minimum inhibitory concentration (MIC) and the assessment of synergism between fluconazole and purified fractions were performed in accordance with the M27-A3 guidelines of Clinical and Laboratory Standards Institute (CLSI, 2008). Results: In the screening test, crude extract and purified fractions were able to inhibit Candida albicans, C. glabrata, C. krusei and C. parapsilosis isolates. Regarding the FPOLIF fraction, MIC values ranging from 7.81 to 15.62 µg/mL against C. glabrata and C. parapsilosis suggested a potential antifungal activity for that fraction. FAQ fraction was also active but to a lesser extent. Nonetheless, both fractions showed a perceptible synergistic effect with fluconazole. A growth inhibitory concentration of 0.98 µg/mL was noticed against C. krusei, the last one a recognized azole-resistant strain. Conclusions: The antifungal activity against pathogenic yeasts and evidence of synergistic activity with fluconazole are first-time reported to Cat’s Claw bioactive derivatives. This finding discloses new research perspectives on the antifungal activity of polyphenols and triterpenes from Cat's Claw bark.