Inhibitory effect of hexameric tannins of proanthocyanidins from Stryphnodendron adstringens stem bark on Candida non-albicans biofilms

Abstract

Yeasts of the Candida genus, human commensal microorganisms, are often associated with opportunistic infections and they can cause mucocutaneous and invasive manifestations. Candida albicans is the most isolated species from clinical material; however Candida non-albicans species (CNA) had increased in the last decades. Among the CNA species, Candida glabrata and Candida krusei are species less susceptible and/or resistant to azole agents. Another complicating factor for antifungal therapy is the ability of Candida spp. to form the biofilms on biotic (tissues) and abiotic (medical and hospital supplies) surfaces, and they are considered the major source of contamination and dissemination. The biofilm cells have shown resistance to the two antifungal agents used in the candidiasis therapy - polyene and azole. The reduced susceptibility to antifungal agents, as well as pharmacokinetic limitations and side effects, lead the search for new antifungals in an attempt to obtain an alternative therapy, and mainly act on the fungal biofilms. Stryphnodendron adstringens, the Brazilian Cerrado plant popularly used as anti-inflammatory agent, healing and treatment of infections in mucosa, has also been proven its pharmacological potential using "in vitro" and "in vivo" models. Among the activities, our research group has shown the antifungal effect on the yeasts Candida and Cryptococcus. We suggested that the hexameric tannins of proanthocyanidins present in the aqueous fraction F2 and subfraction F2.4 obtained from this plant bark have inhibitory effect on both planktonic and biofilm cells of C. albicans (ATCC 10231) (part of the data was obtained from Processo FAPESP 2013/11232-0). Thus, the aim of this work is to continue the project initiated by our group using CNA species of clinical material (C. albicans - reference, C. glabrata, C. krusei, C. parapsilosis and C. topicalis), and finalizing the anti-biofilm evaluation of hexameric tannins obtained from S. adstringens stem bark. (AU)