Óleos essenciais como alternativa inovadora para o tratamento da esporotricose

Abstract

Sporotrichosis is a subcutaneous mycosis with subacute to chronic evolution that can affect humans and animals. Distributed worldwide, it is more prevalent in tropical and temperate climates, being the most common subcutaneous mycosis in South America. Its etiological agents are fungi of the Sporothrix schenckii complex, saprophytic and dimorphic, found in the environment. In Brazil, the exponential increase in cases in humans and animals has been observed in recent decades. In the surroundings of the state of Rio de Janeiro, an epidemic of zoonotic origin is already observed. Allied to this, the treatment of this mycosis has been cause of concern. The high cost and toxicity of the drugs, the prolonged treatment time, and the emergence of resistant strains on drugs of choice justify the growing demand for the discovery of new drugs. In this context, the present study aims to identify the components of the essential oils of Myrtus communis L. and Thymus vulgaris L., to investigate their antifungal potentials in vitro against the main sporotrichosis strains in Brazil, and to determine the preliminary cytotoxicity of essential oils. The essential oils of myrtle and thyme were obtained commercially. The chromatographic profile obtained by GC for the two oils showed high values of monoterpere, 87.1% for myrtle and 98.8% for thyme, with 1-8 cineole and thymol, respectively. The following fungal strains were used: Sporothrix schenckii ATCC 1099-18, Sporothrix schenckii IPEC 15383, Sporothrix brasiliensis ATCC 5110 and Sporothrix brasiliensis IPEC 17943 and two clinical strains of Sporothrix schenckii, referred as A and B. Myrtle essential oil showed antifungal activity against all strains at concentrations ranging from 31.25 to 62.5 μg / mL. Fungicidal activity against all strains was observed at concentrations above 62.5 μg / mL. Thyme essential oil was able to inhibit all lineages at concentrations ranging from 125 to 250 μg / ml. Fungicidal activity was observed against all strains at concentrations above 250 μg / mL. Amphotericin B and itraconazole were used as standard drugs. For these, it was observed that only two of the studied strains showed susceptibility to amphotericin B and itraconazole, all strains studied were considered resistant, with MIC values > 16 μg / mL. These results suggest evidence of fungal resistance of the lines studied in relation to the reference drugs used in the treatment of sporotrichosis. Scanning electron microscopy of fungal lines revealed that, both in the fungi exposed to the experimental treatments and in those exposed to the reference drugs, deformities in the fungal structure when compared to the untreated group were observed. In relation to the cytotoxicity assays performed with human keratinocytes (HACAT) by the MTT reduction method, the oils did not present cytotoxicity at concentrations equivalent to their MIC values.