Desenvolvimento e avaliação da atividade antifúngica de formulação microemulsionada para o tratamento de onicomicoses contendo óleos essenciais de Melissa officinalis L. E Cymbopogon citratus (DC.) Stapf

Abstract

Onychomycosis is a fungal infection of worldwide distribution that causes nail destruction (aesthetic damage) and may impair the patient's social quality of life, interfering in his self-esteem and functional capacity. The disease main causative agents are Candida albicans and Trichophyton rubrum. Currently, the fungal resistance to the drugs present in the market is a problem that has stimulated the research for new drugs to treat this infection, and essential oils have been shown to contain potentially antifungal substances. Thus, this work had as main objective to develop microemulsion formulations containing essential oils for the treatment of onychomycosis. Initially, the eight plants essential oils activity was tested: Aniba parviflora, Aniba rosaeodora, Aniba canelilla, Ocotea cymbarum, Melissa officinalis, Cymbopogon citratus, Piper nigrum and Cinnamomum camphora, against ATCC strains of T. rubrum and C. albicans. The adopted method was broth microdilution The most active oils against fungi were M. officinalis (m) and C. citratus (c), which had minimum inhibitory concentrations (MICs) between 400 and 800 μg.mL-1 and were therefore selected to be incorporated in the microemulsions (MEs). Before, the miscibility test was performed to verify if such essential oils would be miscible in the inputs chosen to compose the systems. Then, microemulsion bases were prepared with different combinations of surfactants (Tween® 20, Tween® 80 and Kolliphor® EL), cosurfactants (Trascutol® P and ethyl and isopropyl alcohols), oil phase (oleic acid) and water, whose proportions were determined by the construction of pseudoternary-ternary phase diagrams, which also enabled the choice of the best MEs regions. The oils (m and c) were then incorporated as oily phases in the base formulations, resulting in a total of twenty MEs which were rescreened in antifungal assay in order to verify and compare the activity of the bases MEs with the MEs containing the essential oils against the studied pathogens. Thus, the five MEs with the highest antifungal action – all containing the oil m (Bm, Em, Gm, Hm, and Im) – were selected and physico-chemical and cytotoxicity tests were performed. The Gm and Hm formulations were considered the best, because in the physicochemical characterization, their viscosity values indicated good fluidity (Gm: 10,43 cP and Hm: 9,0 cP); transparency, since they presented refractive indexes (Gm: 1,380 and Hm: 1,379) and transmittance (Gm: 99.50% and Hm: 99.23%), close to that of water; the electrical conductivity values confirmed that they are O/A types MEs (Gm: 55.7 μS.cm- 1 and Hm: 76.8 μS.cm-1); their droplet sizes (Gm: 81.9 nm and Hm: 108.0 nm); their polydispersity indexes (Gm: 0.239 and Hm: 0.215) and zeta potential values (Gm: -0.50 mV and Hm: -4.73 mV) confirmed their stabilities and; their pH values (Gm: 4.39 and Hm: 4.13) were compatible with that of the skin and nail. The cytotoxicity test was performed on human lung fibroblasts and it was found that the MEs Gm and Hm are non-toxic (IC50%> 50 μg.mL-1). Therefore, the study obtained two promising microemulsion formulations for the topical treatment of onychomycoses caused by T. rubrum and C. albicans.