Chemical-biological prospection of the hydroethanolic extracts of Astronium urundeuva leaves in the investigation of the antifungal potential

Author(s)

Bruna Vidal Bonifácio

• Document type: Doctoral Thesis
• Press: Araraquara. 2019-06-07.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Farmacêuticas. Araraquara
• Defense date: 2018-01-25
• Advisor: Taís Maria Bauab

Abstract

Despite the great technological advances directed to the pharmaceutical industry, microorganisms continue to acquire more and more resistance to the drugs conventionally used in the therapy, and researchers from several areas keep searching new natural antimicrobial sources, such as medicinal plants. Among fungal infections, we highlight those caused by yeasts from the genus Candida sp., for example vulvovaginal candidiasis (VVC). Astronium urundeuva (Allemao) Engl. plant has various biological properties, including antifungal activity. This work aimed to improve the researches directed to the antifungal activity of this medicinal plant in order to investigate the substances responsible for this biological property using bioassay-guided fractionation technique. Among the major components identified in the extract (gallic acid, methyl gallate and ethyl gallate), we could observe that the substances ethyl gallate and methyl gallate are responsible a large part of the antifungal activity against C. glabrata species whereas the activity against C. albicans species seems to be related to a synergistic effect of the components of the extract, including the minority ones. The in vivo results confirmed the antifungal activity exhibited by the extract, but, in addition, showed a better activity of the extract loaded into a microemulsion (ME), confirming the in vitro fungicidal effect presented by it. The cytotoxicity assays (IC50) performed for VERO, MRC5 and HaCaT cell lines showed that the extract were not cytotoxic when compared to the positive control (doxorubicin). In addition, after loaded into the ME, the selectivity index (SI) significantly increased, especially when analyzed for the VERO cell line. When tested against clinical isolates of both species of Candida sp., the free extract showed really effective activity, even against those considered resistant to the drugs conventionally used in clinical therapy (fluconazole, amphotericin B and caspofungin). In addition to the susceptibility test for planktonic cells, the plant sample was also evaluated for its anti-biofilm activity and, although it did not show activity in preformed biofilms at the concentrations that were tested, the free extract was able to inhibit the biofilm formation of C. albicans SC5314 at the same effective concentration for planktonic cells. The combination study, evaluated by the checkerboard assay, showed synergism when the free extract was combined with fluconazole against both species of Candida sp. In addition, the synergistic effect was also observed when amphotericin B was combined with the free extract (against C. albicans) and the ethyl gallate (against C. glabrata). After the serial passage assay, it was observed that the strains developed resistance only to fluconazole, but not to the free extract. In addition to the genus Candida sp., the plant sample was also tested against the genus Cryptococcus sp., highlighting the results presented for C. neoformans WSA and, among some filamentous fungi that were tested, the plant sample was only effective against Rhizopus arrhizus. The results showed that A. urundeuva leaves extract presents promising antifungal activity against Candida species, especially for C. glabrata. (AU)

• FAPESP's process: 13/25121-5 - Chemical-biological prospecting of hydroethanolic extracts of leaves from Astronium urundeuva in the investigation of the antifungal potential
• Grantee: Bruna Vidal Bonifácio
• Support Opportunities: Scholarships in Brazil - Doctorate