Atividade antifúngica de compostos derivados do ácido cinâmico no tratamento da onicomicose

Abstract

Pharmacological treatment of onychomycosis is usually extended, halfhearted, high cost and can brings adverse reactions. In 25 % of cases, this therapy has no satisfactory answer. All of these factors lead to the search for new compounds for therapeutic use. Thus, this study aimed to evaluate the antifungal activity of cinnamaldehyde, eugenol, and α-methyl-trans-cinnamaldehyde and develop a formulation for the treatment against the main causative fungi of onychomicosis. It was evaluated the antifungal activity of compounds, at concentration of 1000 µg/mL against Trichophyton mentagrophytes ATTC 11481; Fusarium oxysporum ATCC 48112, Fusarium solani ATCC 36031, Microsporum canis ATCC 32903, Microsporum gypseum ATCC14683, Trichophyton rubrum URM 1666 and Epidermophyton floccosum CCF-IOC-3757. In addition, it was established the minimum inhibitory concentration (MIC), between the 0.12 to 1000 µg/mL for filamentous fungi cited and Trichophyton mentagrophytes clinical strain and 2.44 to 5000 µg/mL for C. albicans ATCC 10231 and C. albicans clinical strain and minimum fungicide concentration (MFC) against the same strains. Ketoconazole, terbinafine, itraconazole and amphotericin B were used as reference drugs. For these drugs and the most promising compound, were observed morphological changes caused on the tested strains by means of scanning electron microscopy. Furthermore, interference with phospholipase activity in C. albicans was evaluated and the acute toxicity test was developed with the use of bio-indicator Daphnia magna. As well, cell viability percentage was measured on L 929 fibroblast, flow cytometry was performed to assess the changes of F. oxysporum and a formulation with 2 % cinnamaldehyde was developed. The results show that cinnamaldehyde was effective against all tested microorganisms, being more active than the other compounds evaluated. It was active against F. oxysporum, F. solani and E. floccosum, which were not inhibited by the reference drugs and more active against T. rubrum. The micrographs showed that cinnamaldehyde caused changes in the structure of filamentous fungi and yeast, which may be indicative of their mechanism of action and caused reduction of phospholipase activity in C. albicans. In acute toxicity tests, the cinnamaldehyde was considered moderately toxic to D. magna and below 1 µg/mL did not interfere with cell viability in L 929 fibroblasts. Flow cytometry showed that cinnamaldehyde caused reduction in the concentration of neutral lipids, cell viability and interfered with mitochondrial activity of F. oxysporum. The formulation prepared was tested in vitro and inhibited T. mentagrophytes, F. oxysporum, M. gypseum and C. albicans. The results are promising, but it is necessary to check the permeability of the active in the formulation and conduct in vivo testing.