Estudo de estabilidade e eficácia de formulação tópica fitoterápica para tratamento de dermatofitose animal

Abstract

Dermatophytosis are fungal diseases and they are caused in animals by microorganisms of the genus Microsporum spp and Trichophyton spp. Tissues containing keratin are affected resulting in ring lesions and alopecia and it can be transmitted to humans.Trying to find alternative natural treatments, the essential oils are notable for having a complex chemical composition and many known pharmacological actions. The objective of this study was to develop a veterinary formulation for topical use with essential oil to treat the dermatophytosis and evaluate its stability. A morphological characterization of the fungi Trichophyton mentagrophytes ATCC 11480, Microsporum canis ATCC 32903 and Microsporum gypseum ATCC 14683 was performed and also the identification and quantification of chemical components of the essential oils of Pimenta pseudocaryophyllus (Gomes) L.R. Landrum and the Eucalyptus smithii and, subsequently , the analysis of their potential antifungal. A topical formulation (anionic cream type O/A) with the oil of P. pseudocaryophyllus was developed and submitted to 50 °C and 90% relative humidity for 3 months to study of accelerated stability. During this period, physical, chemical and organoleptic parameters of the formulation were evaluated, in addition to thermoanalytical, infrared spectroscopic and gas chromatography (GC) study. The results for P. pseudocaryophyllus were more promising indicating a minimum inhibitory concentration (MIC) of 250 μg mL-1 for all three fungi and minimum fungicidal concentration (MFC) of 250 μg mL-1 for M. canis and 1000 μg mL-1 for T. mentagrophytes and M. gypseum. The formulation containing the oil of P. pseudocaryophyllus with a concentration of 1% (w/w) was effective in combating fungal and, by scanning electron microscopy (SEM), the main morphological changes in hyphae and fungal macroconidia caused by oils and the formulation were observed. During stability study, the formulation was stable in relation to physical, chemical and organoleptic parameters, with only a loss in eugenol concentration (major compound of the essential oil) confirmed by GC. It was possible to verify, by thermoanalytical techniques, the thermal stability and to evaluate the compatibility of the excipients and the essential oil. In general, the results of formulation were satisfactory, but it´s important to emphasize that the thermoanalytical studies does not replace conventional stability studies. To evaluate the real toxicity of this formulation, safety tests need to be performed before to marketing the product.