Bruna Pippi

In vitro evaluation of the acquisition of resistance, antifungal activity and synergism of Brazilian red propolis with antifungal drugs on Candida spp.

To evaluate the ability of Candida parapsilosis and Candida glabrata to develop phenotypic resistance to a benzophenone enriched fraction obtained from Brazilian red propolis (BZP‐BRP) as compared to fluconazole (FLC). To investigate possible synergy between BZP‐BRP and FLC and anidulafungin (AND).

Antifungals discovery: an insight into new strategies to combat antifungal resistance

Undeniably, new antifungal treatments are necessary against pathogenic fungi. Fungal infections have significantly increased in recent decades, being highlighted as important causes of morbidity and mortality, particularly in immunocompromised patients. Five main antifungal classes are used: (i) azoles, (ii) echinocandins, (iii) polyenes, (iv) allylamines and (v) pyrimidine analogues. Moreover, the treatment of mycoses has several limitations, such as undesirable side effects, narrow activity spectrum, a small number of targets and fungal resistance, which are still of major concern in clinical practice. The discovery of new antifungals is mostly achieved by the screening of natural or synthetic/semisynthetic chemical compounds. The most recent discoveries in drug resistance mechanism and their avoidance were explored in a review, focusing on different antifungal targets, as well as new agents or strategies, such as combination therapy, that could improve antifungal therapy.

Evaluation of 8-Hydroxyquinoline Derivatives as Hits for Antifungal Drug Design

Abstract Clioquinol is an 8‐hydroxyquinoline derivative that was widely used from the 1950s to 1970s as an oral antiparasitic agent. In 1970, the oral forms were withdrawn from the market due to reports of toxicity, but topical formulations for antifungal treatment remained available. Thus, the purpose of this study was to evaluate the toxicity, anti‐Candida and antidermatophyte activity and to determine pharmacodynamic characteristics of clioquinol and other 8‐hydroxyquinoline derivatives (8‐hydroxy‐5‐quinolinesulfonic acid and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid). Antifungal activity was tested by broth microdilution and the fungicidal or fungistatic effect was checked by a time‐kill assay. Permeation and histopathological evaluation were performed in Franz diffusion cells with ear skin of pigs and examined under light microscopy. An HET‐CAM test was used to determine the potential irritancy. The three compounds were active against all isolates showing anti‐Candida and antidermatophyte activity, with MIC ranges of 0.031‐2 &mgr;g/ml, 1‐512 &mgr;g/ml, and 2‐1024 &mgr;g/ml for clioquinol, 8‐hydroxy‐5‐quinolinesulfonic acid, and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid, respectively. All compounds showed fungistatic effect for Candida, 8‐hydroxy‐5‐quinolinesulfonic acid, and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid showed a fungicidal effect for M. canis and T. mentagrophytes, and clioquinol showed a fungicidal effect only for T. mentagrophytes. Furthermore, they presented a fungicidal effect depending on the time and concentration. The absence of lesions was observed in histopathological evaluation and no compound was irritating. Moreover, clioquinol and 8‐hydroxy‐5‐quinolinesulfonic acid accumulated in the epithelial tissue, and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid had a high degree of permeation. In conclusion, 8‐hydroxyquinoline derivatives showed antifungal activity and 8‐hydroxy‐5‐quinolinesulfonic acid demonstrated the potential for antifungal drug design.

Reversal of fluconazole resistance induced by a synergistic effect with Acca sellowiana in Candida glabrata strains

Abstract Context: The increased incidence of non-albicans Candida (NAC) resistant to fluconazole (FLZ) makes it necessary to use new therapeutic alternatives. Acca sellowiana (O.berg) Burret (Myrtaceae) is a guava with several proven biological activities. The interaction with fluconazole can be a feasible alternative to overcome this resistance. Objective: This study evaluates the in vitro antifungal activity of fractions obtained from the lyophilized aqueous extract of the leaves of A. sellowiana against resistant strains of NAC. Materials and methods: The antifungal activity of the fractions was evaluated at 500 μg/mL by microdilution method. Checkerboard assay was performed to determine the effect of the combination of the F2 fraction and antifungal at concentrations: MIC/4, MIC/2, MIC, MIC × 2 and MIC × 4. Results: Candida glabrata showed the lowest MIC values (500–3.90 μg/mL) and the F2 active fraction was the most effective. The association of F2 with FLZ showed a strong synergistic effect (FICI ≤ 0.5) against 100% of C. glabrata resistant isolates. Moreover, the F2 active fraction has demonstrated that probably acts in the cell wall of these yeasts. There was no observed acute dermal toxicity of lyophilized aqueous extract of leaves of A. sellowiana on pig ear skin cells. Discussion and conclusion: The interaction between substances present in the F2 active fraction is possibly responsible for the antifungal activity presented by this fraction. This study is unprecedented and suggests that the combination of F2 active fraction and FLZ might be used as an alternative treatment for mucocutaneus infections caused by C. glabrata resistant.

New insights into the mechanism of antifungal action of 8-hydroxyquinolines

The 8-hydroxyquinoline core is a privileged scaffold for drug design explored to afford novel derivatives endowed with biological activity. Our research aimed at clarifying the antifungal mechanism of action of clioquinol, 8-hydroxy-5-quinolinesulfonic acid, and 8-hydroxy-7-iodo-5-quinolinesulfonic acid (three 8-hydroxyquinoline derivatives). The antifungal mode of action of these derivatives on Candida spp. and dermatophytes was investigated using sorbitol protection assay, cellular leakage effect, ergosterol binding assay, and scanning electron microscopy. Clioquinol damaged the cell wall and inhibited the formation of pseudohyphae by C. albicans. The 8-hydroxy-5-quinolinesulfonic acid derivatives compromised the functional integrity of cytoplasmic membranes. To date no similar report was found about the antifungal mechanism of 8-hydroxyquinolines. These results, combined with the broad antifungal spectrum already demonstrated previously, reinforce the potential of 8-hydroxyquinolines for the development of new drugs.

In vitro synergism of a water insoluble fraction of Uncaria tomentosa combined with fluconazole and terbinafine against resistant non-Candida albicans isolates

Abstract Context: Uncaria tomentosa D.C. (Rubiaceae) has several biological activities, including activity against resistant Candida strains. The synergistic interaction with terbinafine or fluconazole can be an important alternative to overcome this resistance. Objectives: The potential synergy between a water insoluble fraction (WIF) from Uncaria tomentosa bark and the antifungals terbinafine (TRB) and fluconazole (FLZ) against non-Candida albicans resistant strains was investigated. Materials and methods: TRB and FLZ, alone and combined with WIF, were tested by the checkerboard procedure using the micro-dilution technique against seven isolates of Candida glabrata and C. krusei. The molecular interactions occurring outside the cell wall were evaluated by scanning electron microscopy, Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC) analysis. Results: The checkerboard inhibitory assay demonstrated synergy for WIF:TRB and WIF:FLZ combinations, respectively. The best synergistic cell damage was demonstrated unequivocally for the associations of WIF and TRB (1.95:4.0 μg/mL) and WIF and FLZ (1.95:8.0 μg/mL). The comparison of the FT-IR spectra of the antifungal alone, and in combination with WIF, allows recognizing clear differences in 3000, 1600, 1400, and 700–800 cm−1 bands. Additionally, modifications on TRB and FLZ thermograms were clearly noticed after their combination with WIF. Conclusions: DSC and infrared analysis demonstrated intermolecular interactions between WIF and either TRB or FLZ. Hence, quite likely the synergistic effect is related to interaction events occurring outside the cell wall between antifungal and cat’s claw proanthocyanidins. A direct action on the cell wall is suggested, without connection with the ABC efflux pump mechanism.

Polyprenylated benzophenone-enriched extracts obtained using SC–CO2 from the dry ethanolic extract of Brazilian red propolis

ABSTRACT Red propolis is a well-known potent antimicrobial source because of its various bioactive compounds. This work aims to submit a sample of Brazilian red propolis to supercritical CO2 extraction, with subsequent chemical characterisation by HPLC and UHPLC–MS, and to evaluate the antifungal activity against three strains of Candida glabrata. The method proved to be selective for the extraction of benzophenones. The results demonstrated a correlation between the presence of benzophenones and antifungal activity. The supercritical extract that seems to be the richest in benzophenones was the one obtained with a pressure of 300 bar and was the most active against the C. glabrata strains. Abbreviations: SFE, Supercritical Fluid Extraction; MIC, Minimal Inhibitory Concentration; SC, Supercritical; BZP, benzophenones

Antifungal mechanism of action of Schinus lentiscifolius Marchand essential oil and its synergistic effect in vitro with terbinafine and ciclopirox against dermatophytes

The aim of this study was to evaluate the antifungal, antichemotactic and antioxidant activities of Schinus lentiscifolius essential oil, as well as its combined effect with terbinafine and ciclopirox, against dermatophytes.

Clioquinol is a promising preventive morphological switching compound in the treatment of Candida infections linked to the use of intrauterine devices

Purpose. Candida biofilm infections are frequently linked to the use of biomaterials and are of clinical significance because they are commonly resistant to antifungals. Clioquinol is an antiseptic drug and is effective against multidrug‐resistant Candida. We investigated the effect of clioquinol and two other 8‐hydroxyquinoline derivatives on Candida biofilm. Methodology. The ability to inhibit biofilm formation, inhibit preformed biofilm and remove established biofilms was evaluated using in vitro assays on microtitre plates. The action of clioquinol on biofilm in intrauterine devices (IUDs) was also investigated, describing the first protocol to quantify the inhibitory action of compounds on biofilms formed on IUDs. Results. Clioquinol was found to be the most effective 8‐hydroxyquinoline derivative among those tested. It prevented more than 90 % of biofilm formation, which can be attributed to blockade of hyphal development. Clioquinol also reduced the metabolic activity of sessile Candida but the susceptibility was lower compared to planktonic cells (0.031‐0.5 &mgr;g ml‐1 required to inhibit 50 % planktonic cells and 4‐16 &mgr;g ml‐1 to inhibit 50 % preformed biofilms). On the other hand, almost complete removal of biofilms was not achieved for the majority of the isolates. Candida spp. also showed the ability to form biofilm on copper IUD; clioquinol eradicated 80‐100 % of these biofilms. Conclusion. Our results indicate a potential application in terms of biomaterials for 8‐hydroxyquinoline derivatives. Clioquinol could be used as a coating to prevent morphological switching and thus prevent biofilm formation. Furthermore, clioquinol may have future applications in the treatment of Candida infections linked to the use of IUDs.

Novas tendências de combate ao biofilme de Candida em próteses dentárias

Apesar de a especie Candida albicans ser efetivamente o microrganismo mais frequentemente associado a estomatite protetica, as especies de Candida nao albicans ja foram isoladas nas superficies de dentaduras e da mucosa oral de individuos com essa lesao eritematosa. A virulencia das especies de Candida e a capacidade de adesao a polimeros acrilicos sao condicoes previas para a colonizacao e o desenvolvimento de biofilmes em superficies de dentaduras. Estudos recentes focam na tentativa de modificacao das resinas acrilicas para diminuir a adesao de cepas patogenicas e formadoras de biofilme do genero Candida spp. Dentro desse aspecto, esta revisao sistematiza o atual panorama epidemiologico da estomatite protetica associada ao uso de proteses dentarias, bem como as atuais e novas opcoes de combate ao biofilme fungico especializado na adesao desse tipo de biomaterial. Palavras-chave: Candida spp.; biofilme; estomatite protetica; resina acrilica; tratamento